Pre-moistened wipe product

ABSTRACT

The present invention provides ion-sensitive, water-dispersible polymers. The present invention also provides a method of making ion-sensitive, water-dispersible polymers and their applicability as binder compositions. The present invention further provides fiber-containing fabrics and webs comprising ion-sensitive, water-dispersible binder compositions and their applicability in water-dispersible personal care products.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation-in-part application of U.S.patent application Ser. No. 09/564,531, filed May 4, 2000.

FIELD OF THE INVENTION

[0002] The present invention provides ion-sensitive, water-dispersiblepolymer formulations. The present invention also provides a method ofmaking ion-sensitive, water-dispersible polymer formulations and theirapplicability as binder compositions for disposable items. The presentinvention further provides disposable items, such as wet-wipescomprising ion-sensitive, water-dispersible binder compositions.

BACKGROUND OF THE INVENTION

[0003] For many years, the problem of disposability has plaguedindustries which provide disposable items, such as, diapers, wet wipes,incontinent garments and feminine care products. While much headway hasbeen made in addressing this problem, one of the weak links has been theinability to create an economical coherent fibrous web, which willreadily dissolve or disintegrate in water, but still have sufficientin-use strength while being safe to contact the user's skin. See, forexample, U.K. patent disclosure 2,241,373 and U.S. Pat. No. 4,186,233.Without such a product, the ability of the user to dispose of theproduct by flushing it down the toilet is greatly reduced, if noteliminated. Furthermore, the ability of the product to disintegrate in alandfill is quite limited because a large portion of the productcomponents, which may well be biodegradable or photodegradable, areencapsulated in or bound together by plastic which degrades over a longperiod of time, if at all. Accordingly, if the plastic disintegrated inthe presence of water, the internal components could degrade as a resultof the rupture of the plastic encapsulation or binding.

[0004] Disposable products, such as diapers, feminine care products andadult incontinent care products may be made to be disposed by flushingdown toilets. Usually such products comprise a body side liner whichmust rapidly pass fluids, such as urine or menses, so that the fluid maybe absorbed by an absorbent core of the product. Typically, the bodyside liner may be a coherent fibrous web, which desirably possesses anumber of characteristics, such as softness and flexibility. The fibrousweb of the body side liner material may be typically formed by wet ordry (air) laying a generally random plurality of fibers and joining themtogether to form a coherent web with a binder compositions. Past bindercompositions have preformed this function well. However, fibrous webscomprising these compositions tended to be non-dispersible and presentproblems in typical household sanitation systems.

[0005] Recent binder compositions have been developed which can be moredispersible and are more environmentally responsible than past bindercompositions. One class of binder compositions includes polymericmaterials having inverse solubility in water. These binder compositionsare insoluble in warm water, but are soluble in cold water, such asfound in a toilet. It is well known that a number of polymers exhibitcloud points or inverse solubility properties in aqueous media. Thesepolymers have been cited in several publications for variousapplications, including (1) as evaporation retarders (JP 6207162); (2)as temperature sensitive compositions, which are useful as temperatureindicators due to a sharp color change associated with a correspondingtemperature change (JP 6192527); (3) as heat sensitive materials thatare opaque at a specific temperature and become transparent when cooledto below the specific temperature (JP 51003248 and JP 81035703); (4) aswound dressings with good absorbing characteristics and easy removal (JP6233809); and (5) as materials in flushable personal care products (U.S.Pat. No. 5,509,913, issued to Richard S. Yeo on Apr. 23, 1996 andassigned to Kimberly-Clark Corporation).

[0006] Other recent binders of interest include a class of binders,which are ion-sensitive. Several U.S. and European patents assigned toLion Corporation of Tokyo, Japan, disclose ion-sensitive polymerscomprising acrylic acid and alkyl or aryl acrylates. See U.S. Pat. Nos.5,312,883, 5,317,063 and 5,384,189, the disclosures of which areincorporated herein by reference, as well as, European Pat. No.608460A1. In U.S. Pat. No. 5,312,883, terpolymers are disclosed assuitable binders for flushable nonwoven webs. The disclosed acrylicacid-based terpolymers, which comprise partially neutralized acrylicacid, butyl acrylate and 2-ethylhexyl acrylate, are suitable binders foruse in flushable nonwoven webs in some parts of the world. However,because of the presence of a small amount of sodium acrylate in thepartially neutralized terpolymer, these binders fail to disperse inwater containing more than about 15 ppm Ca²⁺ and/or Mg²⁺. When placed inwater containing more than about 15 ppm Ca²⁺ and/or Mg²⁺ ions, nonwovenwebs using the above-described binders maintain a tensile strengthgreater than 30 g/in, which negatively affects the “dispersibility” ofthe web. The proposed mechanism for the failure is that each calcium ionbinds with two carboxylate groups either intramolecularly orintermolecularly. Intramolecular association causes the polymer chain tocoil up, which eventually leads to polymer precipitation. Intermolecularassociation yields crosslinking. Whether intramolecular orintermolecular associations are taking place, the terpolymer is notsoluble in water containing more than about 15 ppm Ca²⁺ and/or Mg²⁺. Dueto the strong interaction between calcium ions and the carboxylategroups of the terpolymer, dissociation of the complex is highly unlikelybecause this association is irreversible. Therefore, the above-describedpolymer that has been exposed to a high Ca²⁺ and/or Mg²⁺ concentrationsolution will not disperse in water even if the calcium concentrationdecreases. This limits the application of the polymer as a flushablebinder material because most areas across the U.S. have hard water,which contains more than 15 ppm Ca²⁺ and/or Mg^(2+.)

[0007] In a co-pending application assigned to Kimberly Clark; i.e.,U.S. patent application Ser. No. 09/223,999, filed Dec. 31, 1998, thedisclosure of which is incorporated herein by reference, there isdisclosed a modification of the acrylic acid terpolymers disclosed inthe above-referenced patents to Lion Corporation. Specifically, U.S.patent application Ser. No. 09/223,999 discloses a sulfonate anionmodified acrylic acid terpolymer which has improved dispersibility inrelatively hard water; e.g., up to 200 ppm Ca²⁺ and/or Mg²⁺, compared tothe unmodified Lion polymers. However, the Lion Corporationion-sensitive polymers of the above-referenced patents and the sulfonateanion modified acrylic acid terpolymers of the co-pending application,when used as binders for personal care products, such as wet wipes,typically have reduced sheet wettability, increased sheet stiffness,increased sheet stickiness, reduced binder sprayability and relativelyhigh product cost.

[0008] Another approach to dispersible personal care products isdisclosed in U.S. Pat. No. 5,281,306 to Kao Corporation of Tokyo, Japan.This patent discloses a water-disintegratable cleansing sheet; i.e., wetwipe, comprising water-dispersible fibers treated with a water-solublebinder having a carboxyl group. The cleansing sheet is treated with acleansing agent containing 5%-95% of a water-compatible organic solventand 95%-5% water. A preferred organic solvent is propylene glycol. Thecleansing sheet retains wet strength and does not disperse in theorganic solvent-based cleansing agent, but disperses in water. Thesheets must have these levels of organic solvents as these solventsensure the in-use wet strength for the sheets. Without the solvents, thesheets would have little in-use wet strength and would not be effectiveas an a wet wipe. However, the use of such high amounts of organicsolvent results in a greasy after-feel when the product is used, andthese organic solvents may cause discomfort to skin in higher amounts.

[0009] Although many patents disclose various ion and temperaturesensitive compositions for water-dispersible or flushable materials,there exists a need for dispersible products possessing softness,flexibility, three dimensionality, and resiliency; wicking andstructural integrity in the presence of body fluids (including feces) atbody temperature; and true fiber dispersion after toilet flushing sothat fibers do not become entangled with tree roots or at bends in sewerpipes. In addition, the known ion-sensitive polymers, such as those ofLion Corporation and the co-pending application of Kimberly Clark, haverelatively high viscosities at high shear rates that make application byspraying impossible or impractical. Moreover, there is a need in the artfor flushable products having water-dispersibility in all areas of theworld, including soft and hard water areas. Furthermore, there is a needfor water-dispersible binders that do not reduce wettability of productwith which they are used and are sprayable for easy and uniformapplication to and penetration into products. Finally, there is a needfor water-dispersible, flushable wet wipes that are stable duringstorage and retain a desired level of wet strength during use and arewetted with a wetting composition that is relatively free, or issubstantially free, of organic solvents. Such a product is needed at areasonable cost without compromising product safety and environmentalconcerns, something that past products have failed to do.

SUMMARY OF THE INVENTION

[0010] The present invention is directed to ion-sensitive polymerformulations, which have been developed to address the above-describedproblems associated with currently available, ion-sensitive polymers andother polymers described in literature. The ion-sensitive polymerformulations of the present invention have a “trigger property,” suchthat the polymers are insoluble in a wetting composition comprising ionsof a particular type and concentration, such as monovalent saltsolutions at a concentration from about 0.3% to 10%, but can be solublewhen diluted with water, including divalent salt solutions such as hardwater with up to 200 ppm (parts per million) calcium and magnesium ions.Unlike some ion-sensitive polymer formulations, which losedispersibility in hard water because of ion cross-linking by calciumions, the polymer formulations of the present invention are relativelyinsensitive to calcium and/or magnesium ions. Consequently, flushableproducts containing the polymer formulations of the present inventionmaintain dispersibility in hard water. Furthermore, the ion-sensitivepolymer formulations of the present invention can have improvedproperties of sprayability or reduced high-shear viscosity, improvedproduct wettability or decreased properties of product stiffness andstickiness.

[0011] The polymer formulations of the present invention are useful asbinders and structural components for air-laid and wet-laid nonwovenfabrics for applications such as body-side liners, fluid distributionmaterials, fluid in-take materials (surge) or cover stock in variouspersonal care products. The polymer formulations of the presentinvention are particularly useful as a binder material for flushablepersonal care products, particularly wet wipes for personal use such ascleaning or treating skin, make-up removal, nail polish removal, medicalcare, and also wipes for use in hard surface cleaning, automotive care,including wipes comprising cleaning agents, disinfectants, and the like.The flushable products maintain integrity or wet strength during storageand use, and break apart or disperse into fibers or small pieces afterdisposal in the toilet when the salt concentration falls below acritical level. Suitable substrates for treatment include tissue, suchas creped or uncreped tissue, coform products, hydroentangled webs,airlaid mats, fluff pulp, nonwoven webs, and composites thereof. Methodsfor producing uncreped tissues and molded three-dimensional tissue websof use in the present invention can be found in commonly owned U.S.patent application Ser. No. 08/912,906, “Wet Resilient Webs andDisposable Articles Made Therewith,” by F. -J. Chen et al., filed Aug.15, 1997; U.S. Pat. No. 5,429,686, issued to Chiu et al. on Jul. 4,1995; U.S. Pat. No. 5,399,412, issued to S. J. Sudall and S. A. Engel onMar. 21, 1995; U.S. Pat. No. 5,672,248, issued to Wendtetal. on Sep. 30,1997; and U.S. Pat. No. 5,607,551, issued to Farrington et al. on Mar.4, 1997; all of which are herein incorporated in their entirety byreference. The molded tissue structures of the above patents can beespecially helpful in providing good cleaning in a wet wipe. Goodcleaning can also be promoted by providing a degree of texture in othersubstrates as well by embossing, molding, wetting and through-air dryingon a textured fabric, and the like.

[0012] Airlaid material can be formed by metering an airflow containingthe fibers and other optional materials, in substantially dry condition,onto a typically horizontally moving wire forming screen. Suitablesystems and apparatus for air-laying mixtures of fibers andthermoplastic material are disclosed in, for example, U.S. Pat. No.4,157,724 (Persson), issued Jun. 12, 1979, and reissued Dec. 25, 1984 asRe. U.S. Pat. No. 31,775; U.S. Pat. No. 4,278,113 (Persson), issued Jul.14, 1981; U.S. Pat. No. 4,264,289 (Day), issued Apr. 28, 1981; U.S. Pat.No. 4,352,649 (Jacobsen et al.), issued Oct. 5, 1982; U.S. Pat. No.4,353,687 (Hosler, et al.), issued Oct. 12, 1982; U.S. Pat. No.4,494,278 (Kroyer, et al.), issued Jan. 22, 1985; U.S. Pat. No.4,627,806 (Johnson), issued Dec. 9, 1986; U.S. Pat. No. 4,650,409(Nistri, et al.), issued Mar. 17, 1987; and U.S. Pat. No. 4,724,980(Farley), issued Feb. 16, 1988; and U.S. Pat. No. 4,640,810 (Laursen etal.), issued Feb. 3, 1987.

[0013] The present invention also discloses how to makewater-dispersible nonwovens, including cover stock (liner), intake(surge) materials and wet wipes, which are stable in fluids having afirst ionic composition, such as monovalent ions at a particularconcentration substantially greater than is found in typical hard water,using the above-described unique polymer formulations as bindercompositions. The resultant nonwovens are flushable andwater-dispersible due to the tailored ion sensitivity, which can betriggered regardless of the hardness of water found in toiletsthroughout the United States and the world. Dispersible products inaccordance with the present invention also can have improved propertiesof softness and flexibility. Such products also have reduced stickiness.In some embodiments, the polymer formulations with which such articlesare treated can have improved properties of sprayability, which improvespolymer distribution on the product and penetration into the product, inaddition to ease of application, which translates into cost savings.

[0014] The present invention further discloses an improved wettingcomposition for wet wipes. Wet wipes employing the polymer formulationsof the present invention are stable during storage and retain a desiredlevel of wet strength during use and are wetted with a wettingcomposition or cleaning agent that can be relatively free, or issubstantially free, of organic solvents.

[0015] The present invention also provides a wet-wipe product thatdisperses in both hard and soft water, while maintaining one or more ofthe following characteristics. The wet wipe desirably has a higher wetopacity than prior art products, thereby increasing consumer confidencein the barrier properties of the product. Also, the wet-wipe product mayhave a higher wet sheet thickness such that the product does not teareasily and provides a barrier between the hand and the surface beingwiped. Finally, the wet-wipe product is desirably soft to the touch ascompared to prior art products.

[0016] These features and advantages of the present invention willbecome apparent after a review of the following detailed description ofthe disclosed embodiments and the appended drawing and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a graph that depicts wet strength data for three binderformulations as a function of ionic environment and soak time.

[0018]FIG. 2 is a chart showing how wet tensile strength (reported asCDWT in grams per 2.54 cm over a range of soak times) can change overtime as a fabric, comprising 68 gsm softwood airlaid webs andion-sensitive binders, are soaked in solutions comprising calcium ions.

[0019]FIG. 3 compares two data sets with Lion SSB-3b product taken fromFIG. 2 (labeled as Code 3300) with a sulfonated salt-sensitive binderblended with Dur-O-Set® RB polymer in a 75/25 ratio.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS

[0020] To be an effective ion-sensitive formulations suitable for use influshable or water-dispersible personal care products, the formulationsshould desirably be (1) functional; i.e., maintain wet strength undercontrolled conditions and dissolve or disperse rapidly in soft or hardwater such as found in toilets and sinks around the world; (2) safe (nottoxic) to contact the user's skin; and (3) relatively economical. Inaddition to the foregoing factors, the ion-sensitive formulations whenused as a binder composition for a non-woven substrate, such as a wetwipe, desirably should be (4) processable on a commercial basis; i.e.,may be applied relatively quickly on a large scale basis, such as byspraying, which thereby requires that the binder composition have arelatively low viscosity at high shear; (5) provide acceptable levels ofsheet or substrate wettability; and (6) provide improved product feel,such as improved softness, wet opacity, wet thickness, productflexibility and reduced stickiness. The wetting composition with whichthe wet wipes of the present invention are treated can provide some ofthe foregoing advantages, and, in addition, can provide one or more of(7) improved skin care, such as reduced skin irritation or otherbenefits, (8) improved tactile properties, and (9) promote good cleaningby providing a balance in use between friction and lubricity on the skin(skin glide). The ion-sensitive polymer formulations of the presentinvention and articles made therewith, especially wet wipes comprisingparticular wetting compositions set forth below, can meet many or all ofthe above criteria. Of course, it is not necessary for all of theadvantages of the preferred embodiments of the present invention to bemet to fall within the scope of the present invention and the presentinvention may provide one or more of these benefits.

[0021] The polymer formulations of the present invention may be formedfrom a single triggerable polymer, such as an ion-sensitive polymer, orfrom a combination of two or more different polymers, such as atriggerable polymer and a co-binder. Desirably, at least one polymer ofthe polymer formulations of the present invention is an ion-sensitivepolymer. Ion-sensitive polymers are known in the art and include anypolymer whose water solubility varies depending on the type and amountof ions present in water. Ion-sensitive polymers useful in the presentinvention include, but are not limited to the Lion polymers discussedabove, such as the Lion acrylic acid terpolymer, the sulfonate anionmodified acrylic acid terpolymer of the co-pending application09/223,999 assigned to Kimberly Clark Worldwide, Inc.; the acrylic acidfree polymers of the co-pending U.S. patent application Ser. No.09/565,623, filed on May 04, 2000 and entitled “Ion-Sensitive Hard WaterDispersible Polymers and Applications Therefor”, also assigned toKimberly Clark Worldwide, Inc.; as well as, other ion- andchemical-sensitive polymers, including the polymers of U.S. Pat. No.6,043,317, issued Mar. 28, 2000 to Mumick et al., and also assigned toKimberly Clark Worldwide, Inc.; the disclosures of which are hereinincorporated by reference in their entirety.

[0022] Other known triggerable polymers include temperature-sensitiveand heat-sensitive polymers, as well as, polymers which becomedispersible in the presence of a dispersion aid added to the water of atoilet bowl or other water source, as discussed in U.S. Pat. No.5,948,710, issued Sep. 7, 1999 to Pomplun et al. and assigned toKimberly Clark Worldwide, Inc., who note that another means forrendering a polymer degradable in water is through the use oftemperature change. Certain polymers exhibit a cloud point temperature.As a result, these polymers will precipitate out of a solution at aparticular temperature, which is the cloud point. These polymers can beused to form fibers, which are insoluble in water above a certaintemperature, but which become soluble and thus degradable in water at alower temperature. As a result, it is possible to select or blend apolymer, which will not degrade in body fluids, such as urine, at ornear body temperature (37° C.) but which will degrade when placed inwater at temperatures below body temperature, for example, at roomtemperature (23° C.). An example of such a polymer ispolyvinylmethylether, which has a cloud point of 34° C. When thispolymer is exposed to body fluids such as urine at 37° C., it will notdegrade as this temperature is above its cloud point (34° C.). However,if the polymer is placed in water at room temperature (23° C.), thepolymer will, with time, go back into solution as it is now exposed towater at a temperature below its cloud point. Consequently, the polymerwill begin to degrade. Blends of polyvinylmethylether and copolymers maybe considered as well. Other cold water soluble polymers includepoly(vinyl alcohol) graft copolymers supplied by the Nippon SyntheticChemical Company, Ltd. of Osaka, Japan, which are coded Ecomaty AX2000,AX10000 and AX300G.

[0023] Ion-Sensitive Polymers

[0024] The ion-sensitive Lion polymers and the ion-sensitive polymers ofthe above-referenced co-pending applications and U.S. patents ofKimberly-Clark Worldwide, Inc. are useful in the present invention. Thesulfonate anion modified acrylic acid terpolymer of co-pending patentapplication Ser. No. 09/223,999, assigned to Kimberly-Clark Worldwide,Inc., are desired because, unlike the Lion Corp. polymers and otherpolymers cited in technical literature, the polymers of the co-pendingapplication Ser. No. 09/223,999 are soluble in water having from lessthan about 10 ppm Ca²⁺ and/or Mg up to about 200 ppm Ca²⁺ and/or Mg²⁺.The polymers of the co-pending application are formulated to minimizethe potentially strong interaction between the anions of the polymersand the cations in the water. This strong interaction can be explainedvia the hard-soft acid-base theory proposed by R. G. Pearson in theJournal of the American Chemical Society, vol. 85, pg. 3533 (1963); orN. S. Isaacs in the textbook, Physical Organic Chemistry, published byLongman Scientific and Technical with John Wiley & Sons, Inc., New York(1987). Hard anions and hard cations interact strongly with one another.Soft anions and soft cations also interact strongly with one another.However, soft anions and hard cations, and vice-versa, interact weaklywith one another. In the Lion polymers, the carboxylate anion of thesodium acrylate is a hard anion, which interacts strongly with the hardcations, Ca²⁺ and/or Mg²⁺, present in moderately hard and hard water. Byreplacing the carboxylate anions with a softer anion, such as asulfonate anion, the interaction between the anions of anion-triggerable polymer and the hard cations, Ca²⁺ and/or Mg²⁺, presentin moderately hard and hard water, is reduced.

[0025] As used herein, the term “soft water” refers to water having adivalent ion content of less than about 10 ppm. As used herein, the term“moderately hard water” refers to water having a divalent ion content offrom about 10 to about 50 ppm. As used herein, the term “hard water”refers to water having a divalent ion content of more than about 50 ppmup to about 200 ppm. By controlling the hydrophobic/hydrophilic balanceand the composition of the polymers as well as the combination ofpolymers forming the formulation, the ion-sensitive polymer formulationshaving desired in-use binding strength and water-dispersibility in waterare produced. The ion-sensitive polymer can be a copolymer, such as aterpolymer.

[0026] Ion-sensitive acrylic acid copolymers of the present inventionmay comprise any combination of acrylic acid monomers and acrylic ester(alkyl acrylate) monomers capable of free radical polymerization into acopolymer and, specifically, a terpolymer. Suitable acrylic acidmonomers include, but are not limited to, acrylic acid and methacrylicacid. Suitable acrylic monomers include, but are not limited to, acrylicesters and methacrylic esters having an alkyl group of 1 to 18 carbonatoms or a cycloalkyl group of 3 to 18 carbon atoms and it is preferredthat acrylic esters and/or methacrylic esters having a alkyl group of 1to 12 carbon atoms or a cycloalkyl group of 3 to 12 carbon atoms be usedsingly or in combination. Other suitable monomers include, but are notlimited to, acrylamide and methacrylamide based monomers, such asacrylamide, N,N-dimethyl acrylamide, N-ethyl acrylamide, N-isopropylacrylamide, and hydroxymethyl acrylamide; N-vinylpyrrolidinone;N-vinylforamide; hydroxyalkyl acrylates and hydroxyalkyl methacrylates,such as hydroxyethyl methacrylate and hydroxyethyl acrylate. Othersuitable acrylic acid monomers and acrylic ester monomers are disclosedin U.S. Pat. No. 5,317,063, assigned to Lion Corporation, Tokyo, Japan,the disclosure of which is incorporated herein by reference in itsentirety. A particularly preferred acrylic acid terpolymer is LIONSSB-3b, available from Lion Corporation. (In alternative embodiments,the ion-sensitive polymer is formed from monomers other than acrylicacid or its derivatives, or is relatively free of acrylic acid,methacrylic acid, and salts thereof.)

[0027] The relative amounts of the monomers in the acrylic acidcopolymer of the present invention may vary depending on the desiredproperties in the resulting polymer. The mole percent of acrylic acidmonomer in the copolymer is up to about 70 mole percent. Morespecifically, the mole percent of acrylic acid monomer in the copolymeris from about 15 to about 50 mole percent. Most specifically, the molepercent of acrylic acid monomer in the copolymer is from about 25 toabout 40 mole percent.

[0028] More specifically, examples of the acrylic acid copolymers usefulin the present invention include copolymers of 10 weight percent to 90weight percent, desirably 20 weight percent to 70 weight percent ofacrylic acid and/or methacrylic acid and 90 weight percent to 10 weightpercent, desirably 80 weight percent to 30 weight percent of acrylicesters and/or methacrylic esters having an alkyl group of 1 to 18 carbonatoms or a cycloalkyl group of 3 to 18 carbon atoms in which 1 to 60mole percent, desirably 5 to 50 mole percent of acrylic acid and/ormethacrylic acid is neutralized to form a salt; or copolymers of 30weight percent to 75 weight percent, desirably 40 weight percent to 65weight percent of acrylic acid, 5 weight percent to 30 weight percent,desirably 10 weight percent to 25 weight percent of acrylic estersand/or methacrylic esters having an alkyl group of 8 to 12 carbon atomsand 20 weight percent to 40 weight percent; desirably 25 weight percentto 35 weight percent of acrylic esters and/or methacrylic esters havingan alkyl group of 2 to 4 carbon atoms in which 1 to 50 mole percent,desirably 2 to 40 mole percent of acrylic acid is neutralized to form asalt.

[0029] The acrylic acid copolymers of the present invention may have anaverage molecular weight, which varies depending on the ultimate use ofthe polymer. The acrylic acid copolymers of the present invention have aweight average molecular weight ranging from about 10,000 to about5,000,000. More specifically, the acrylic acid copolymers of the presentinvention have a weight average molecular weight ranging from about25,000 to about 2,000,000, or, more specifically still, from about200,000 to about 1,000,000.

[0030] The acrylic acid copolymers of the present invention may beprepared according to a variety of polymerization methods, desirably asolution polymerization method. Suitable solvents for the polymerizationmethod include, but are not limited to, lower alcohols such as methanol,ethanol and propanol; a mixed solvent of water and one or more loweralcohols mentioned above; and a mixed solvent of water and one or morelower ketones such as acetone or methyl ethyl ketone.

[0031] In the polymerization methods of the present invention, anypolymerization initiator may be used. Selection of a particularinitiator may depend on a number of factors including, but not limitedto, the polymerization temperature, the solvent, and the monomers used.Suitable polymerization initiators for use in the present inventioninclude, but are not limited to, 2,2′-azobisisobutyronitrile,2,2′-azobis(2-methylbutyronitrile),2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobis(2-amidinopropane)dihydrochloride,2,2′-azobis(N,N′-dimethyleneisobutylamidine), potassium persulfate,ammonium persulfate, and aqueous hydrogen peroxide. The amount ofpolymerization initiator may desirably range from about 0.01 to 5 weightpercent based on the total weight of monomer present.

[0032] The polymerization temperature may vary depending on thepolymerization solvent, monomers, and initiator used, but in general,ranges from about 20° C. to about 90° C. Polymerization time generallyranges from about 2 to about 8 hours.

[0033] The sulfonate anion modified acrylic acid copolymers inaccordance with the present invention include hydrophilic monomers, suchas acrylic acid or methacrylic acid, incorporated into the acrylic acidcopolymers of the present invention along with one or moresulfonate-containing monomers. The sulfonate anions of these monomersare softer than carboxylate anions since the negative charge of thesulfonate anion is delocalized over three oxygen atoms and a largersulfur atom, as opposed to only two oxygen atoms and a smaller carbonatom in the carboxylate anion. These monomers, containing the softersulfonate anion, are less interactive with multivalent ions present inhard water, particularly Ca²⁺ and Mg²⁺ ions. Suitablesulfonate-containing monomers include, but are not limited to,2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and organic orinorganic salts of 2-acrylamido-2-methyl-1-propanesulfonic acid, such asalkali earth metal and organic amine salts of2-acrylamido-2-methyl-1-propanesulfonic acid, particularly the sodiumsalt of 2-acrylamido-2-methyl-1-propanesulfonic acid (NaAMPS).Additional suitable sulfonate-containing monomers include, but are notlimited to, 2-methyl-2-propene sulfonic acid, vinyl sulfonic acid,styrene sulfonic acid, 2-sulfopropyl methacrylate and 3-sulfopropylacrylate, and organic or inorganic salts thereof, such as alkali earthmetals and organic amine salts, such as alkyl ammonium hydroxide whereinthe alkyl groups are C₁-C₁₈. To maintain the hydrophobic/hydrophilicbalance of the ion-sensitive polymer, one or more hydrophobic monomersare added to the polymer.

[0034] The ion-sensitive sulfonate anion modified acrylic acidcopolymers of the present invention may be produced from monomersincluding the following monomers: acrylic acid, methacrylic acid, or acombination thereof; 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS)and organic or inorganic salts thereof, such as the sodium salt thereof(NaAMPS); butyl acrylate; and 2-ethylhexyl acrylate. Desirably, theion-sensitive sulfonate anion modified acrylic acid copolymers of thepresent invention are produced from: acrylic acid; AMPS, NaAMPS or acombination thereof; butyl acrylate; and 2-ethylhexyl acrylate.Desirably, the monomers are present in the sulfonate anion modifiedacrylic acid copolymer at the following mole percents: acrylic acid,about 35 to less than 80 mole percent; AMPS or NaAMPS, greater than 0 toabout 20 mole percent; butyl acrylate, from greater than 0 to about 65mole percent; and 2-ethylhexyl acrylate, from greater than 0 to about 45mole percent. More specifically, the monomers are present in thesulfonate anion modified acrylic acid copolymer at the following molepercents: acrylic acid, about 50 to about 67 mole percent; AMPS orNaAMPS, from greater than 0 to about 10 mole percent; butyl acrylate,from about 15 to about 28 mole percent; and 2-ethylhexyl acrylate, fromabout 7 to about 15 mole percent. Most specifically, the monomers arepresent in the sulfonate anion modified acrylic acid copolymer at thefollowing mole percents: acrylic acid, about 57 to about 66 molepercent; AMPS or NaAMPS, from about 1 to about 6 mole percent; butylacrylate, from about 15 to about 28 mole percent; and 2-ethylhexylacrylate, from about 7 to about 13 mole percent; especially, about 60mole percent acrylic acid, about 5 mole percent AMPS or NaAMPS, about24.5 mole percent butyl acrylate and about 10.5 mole percent2-ethylhexyl acrylate.

[0035] If AMPS is used as one of the monomers, it is desired toneutralize at least a portion of the acid component. Any inorganic baseor organic base may be used as a neutralizing agent to neutralize theacid component. Examples of neutralizing agents include, but are notlimited to, inorganic bases, such as sodium hydroxide, potassiumhydroxide, lithium hydroxide and sodium carbonate, and amines, such asmonoethanolamine, diethanolamine, diethylaminoethanol, ammonia,trimethylamine, triethylamine, tripropylamine, morpholine. Preferredneutralizing agents include sodium hydroxide, potassium hydroxide, or acombination thereof.

[0036] A sulfonate modified copolymer having salt-sensitivity may alsobe produced by sulfonation of an existing polymer, such as a copolymeror acrylic acid-derived terpolymer. Methods of sulfonating polymers arewell known in the art. Methods for the production of sulfonated orsulfated polymers are disclosed in U.S. Pat. No. 3,624,069, issued Nov.1971 to Schwelger; U.S. Pat. No. 4,419,403, issued Dec. 6, 1983 toVarona; U.S. Pat. No. 5,522,967, issued Jun. 4, 1996 to Shet; U.S. Pat.No. 4,220,739, issued Sep. 2, 1980 to Walles, U.S. Pat. No. 5,783,200,issued Jul. 21, 1998 to Motley et al., as well as the following patents:U.S. Pat. Nos. 2,400,720; 2,937,066; 2,786,780; 2,832,696; 3,613,957,and 3,740,258, all of which are herein incorporated by reference.Principles for sulfation and sulfonation (e.g., via sulfamic acidtreatment, reaction with thionyl chloride or chlorosulfonic acid, orexposure to sulfur trioxide) are among the pathways disclosed by SamuelShore and D. R. Berger in “Alcohol and Ether Alcohol Sulfates,” inAnionic Surfactants, Part 1, ed. Warner M. Linfield, N.Y.: MarcelDekker, Inc., 1976, pp. 135-149; and by Ben E. Edwards, “The Mechanismsof Sulfonation and Sulfation,” in Anionic Surfactants, Part 1, ed.Warner M. Linfield, N.Y.: Marcel Dekker, Inc., 1976, pp. 111-134, bothof which are herein incorporated by reference.

[0037] In a further embodiment of the present invention, theabove-described ion-sensitive polymer formulations are used as bindermaterials for flushable and/or non-flushable products. To be effectiveas a binder material in flushable products throughout the United States,the ion-sensitive polymer formulations of the present invention remainstable and maintain their integrity while dry or in relatively lowconcentrations of monovalent ions, but become soluble in watercontaining up to about 200 ppm divalent ions, especially calcium andmagnesium ions. As such, products having this binder will be dispersiblein both low, i.e. about 10 ppm, and high, i.e. about 200 ppm, divalention concentrations, unlike the products of the prior art.

[0038] Desirably, the ion-sensitive polymer formulations of the presentinvention including acrylic acid copolymers are insoluble in a saltsolution containing at least about 0.3 weight percent of one or moreinorganic and/or organic salts containing monovalent ions. Moredesirably, the ion-sensitive polymer formulations of the presentinvention including acrylic acid copolymers are insoluble in a saltsolution containing from about 0.3 weight percent to about 5.0 weightpercent of one or more inorganic and/or organic salts containingmonovalent ions. Even more desirably, the ion-sensitive polymerformulations of the present invention including acrylic acid copolymersare insoluble in salt solutions containing from about 1 weight percentto about 3.0 weight percent of one or more inorganic and/or organicsalts containing monovalent ions. Suitable monovalent ions include, butare not limited to, Na⁺ ions, K⁺ ions, Li⁺ ions, NH₄ ⁺ ions, lowmolecular weight quaternary ammonium compounds (e.g., those having fewerthan 5 carbons on any side group), and a combination thereof.

[0039] In an alternate embodiment, the ion-sensitive polymerformulations of the present invention including sulfonate anion modifiedacrylic acid copolymers are insoluble in a salt solution containing atleast about 1 weight percent of one or more inorganic and/or organicsalts containing monovalent ions. More desirably, the ion-sensitivepolymer formulations of the present invention including sulfonate anionmodified acrylic acid terpolymers are insoluble in a salt solutioncontaining from about 1.0 weight percent to about 5.0 weight percent ofone or more inorganic and/or organic salts containing monovalent ions.Even more desirably, the ion-sensitive polymer formulations of thepresent invention including sulfonate anion modified acrylic acidterpolymers are insoluble in salt solutions containing from about 1.0weight percent to about 3.0 weight percent of one or more inorganicand/or organic salts containing monovalent ions. Suitable monovalentions include, but are not limited to, Na⁺ ions, K⁺ ions, Li⁺ ions, NH₄ ⁺ions, low molecular weight quaternary ammonium compounds (e.g., thosehaving fewer than 5 carbons on any side group), and a combinationthereof.

[0040] Based on a recent study conducted by the American ChemicalSociety, water hardness across the United States varies greatly, withCaCO₃ concentration ranging from near zero for soft water to about 500ppm CaCO₃ (about 200 ppm Ca²⁺ ion) for very hard water. To ensurepolymer formulation dispersibility across the country (and throughoutthe whole world), the ion-sensitive polymer formulations of the presentinvention are desirably soluble in water containing up to about 50 ppmCa²⁺ and/or Mg²⁺ ions. More desirably, the ion-sensitive polymerformulations of the present invention are soluble in water containing upto about 100 ppm Ca²⁺ and/or Mg²⁺ ions. Even more desirably, theion-sensitive polymer formulations of the present invention are solublein water containing up to about 150 ppm Ca²⁺ and/or Mg²⁺ ions. Even moredesirably, the ion-sensitive polymer formulations of the presentinvention are soluble in water containing up to about 200 ppm Ca²⁺and/or Mg²⁺ ions.

[0041] A wide variety of polymer/surfactant systems may be used toprovide the same functionality as the ion-sensitive Lion polymers andthe ion-sensitive sulfonate anion modified acrylic acid terpolymers ofco-pending patent application Ser. No. 09/223,999, without the need tobe limited to sulfonic or carboxylic moieties. Such other systems aredescribed below.

[0042] Phosphorylated polymers containing phosphonic groups,thiophsulphonic groups, or other organophosphorous groups as the “soft”anion capable of establishing a mismatch with Ca⁺⁺ may be used as theion-sensitive polymer in the present invention. This can includemodified cellulose or cellulose derivatives and related gums, madeinsoluble by the presence of monovalent salts or other electrolytes. Inone embodiment, soluble cellulose derivatives, such as CMC, arephosphorylated and rendered insoluble and can be effective asion-sensitive polymer formulations when in a solution of high ionicstrength or of appropriate pH, but are dispersible in tap water. Inanother embodiment, aminophosphinic groups which can be anionic oramphoteric, are added to a polymer. Aminophosphinic groups can be addedvia condensation of a hypophosphite salt with a primary amine. Reactionof chloromethylphosphinic acid with amines can also yield useful anionicgroups, as described by Guenther W. Wasow in “Phosphorous-ContainingAnionic Surfactants,” Anionic Surfactants: Organic Chemistry, ed. HelmutW. Stache, N.Y.: Marcel Dekker, 1996, pp. 589-590. The entire chapter byWasow, comprising pages 551-629 of the aforementioned book, offersadditional teachings relevant to creating polymers with usefulphosphorous groups, and is herein incorporated by reference.

[0043] Other methods of preparing phosphorylated cellulose fibers arewell known. These methods may be adapted to CMC, which may then serve asa binder agent. Exemplary methods are disclosed in U.S. Pat. No.3,739,782, issued Jun. 19, 1973 to Bernardin. Cellulose and synthetic ornatural polymers modified to have other “soft” anionic groups can beuseful as the ion-sensitive polymer of the present invention.

[0044] Natural polymers that are already provided with useful anionicgroups also can be useful in the present invention. Such polymersinclude agar and carageenan, which have multiple ester sulfate groups.These may be further modified, if necessary, to have additional anionicgroups (e.g., sulfonation, phosphorylation, and the like).

[0045] Polymers having two or more differing soft anionic groups, suchas both sulfonic and phosphonic groups, wherein the relative amounts ofthe differing anions can be adjusted to optimize the strength, the ionicsensitivity, and the dispersibility of the polymer, are also useful inthe present invention. This also includes zwitterionic and amphotericcompounds. Polyampholytes in particular can be readily soluble above orbelow the isoelectric point, but insoluble at the isoelectric point,offering the potential for a triggering mechanism based on electrolyteconcentration and pH. Examples of polyampholytes include, but are notlimited to, copolymers of methacrylic acid and allylamine, copolymers ofmethacrylic acid and 2-vinylpyridine, polysiloxane ionomers with pendantamphoteric groups, and polymers formed directly from zwitterionicmonomeric salts, such as the ion-pair of co-monomers (IPC) of Salamoneet al., all as disclosed by Irja Piirma in Polymeric Surfactants, NewYork: Marcel Dekker, Inc., 1992, at pp. 251-254, incorporated herein byreference.

[0046] Proteins capable of being salted out, optionally modified to haveadditional soft ionic groups, can be useful as the ion-sensitive polymerof the present invention.

[0047] Systems such as those comprising algin derivatives or naturalsulfonated polymers in which calcium ion in high concentrations (muchhigher than the levels of 250 ppm or less that may be encountered inhard water) insolubilize the binder, but allow even hard water tosufficiently dilute the calcium ion to render the binder dispersible areuseful in the present invention. Thus, while it is desired that theion-sensitive binders of the present invention be insoluble in solutionscomprising a monovalent metal ion above a critical concentration, insome embodiments useful ion-sensitive binders are insoluble in solutionscomprising a divalent metal ion above a critical concentration, butbecome soluble when the divalent metal ion concentration falls to about200 ppm or more specifically to about 100 ppm, such that a fibroussubstrate with the ion-sensitive polymer as a binder maintains good wetstrength in a solution comprising an elevated concentration of thedivalent metal ion, yet becomes water dispersible in hard water ormedium hard water. Thus, the triggering mechanism, which results in apre-moistened wipe losing wet strength and becoming flushable even inhard water, can be due to the dilution of a monovalent or divalent metalion, and particularly an alkali metal ion, with monovalent ions, such assodium being preferred. Natural polymers and gums, which may be adaptedfor use as ion-sensitive binders, are described by R. L. Whistler and J.N. BeMiller in Industrial Gums, New York: Academic Press, Inc., 1973,incorporated herein by reference. Natural polymers, which become firm orform a gel in the presence of calcium ions, are described below.

[0048] Algin (which may need to be in the form of sodium alginate andcalcium alginate for good dispersibility, based on reported behavior inuse a binder for medicinal tablets—see p. 62 of Whistler and BeMiller),which is insoluble as alginic acid, calcium alginate, or in general as asalt of most polyvalent metals, but soluble as sodium alginate or as asalt with low-molecular-weight amines or quaternary ammonium compounds(p. 67) may be useful in the present invention. This material may beused, especially when zinc is an insolubilizing metal ion.

[0049] Other useful polymers include Carageenan and Iridophycan, bothseaweed derivatives comprising ester sulfates.

[0050] Both natural polymers, including cellulose, and syntheticpolymers can be provided with anionic groups, such as sulfonic groups,phosphonic groups, and carboxyl groups, capable of forming bridges toother molecules in the presence of ions of a suitable type andconcentration. When the ionic concentration is substantially changed,such as by placing a cleansing article of the present invention in atoilet bowl, the article may become weak and disintegrate.

[0051] Ion-sensitive polymers include those which are dispersible inaqueous environment under prescribed conditions, yet are not dispersiblein all aqueous environments. Examples include materials that arealkaline dispersible or saline insoluble. The Eastman AQ copolyesters(Eastman Chemical Company, Kingsport, Tenn.), for example, can bedispersible in deionized water yet insoluble in saline solutions. Theyhave been proposed for use in articles such as diapers intended toabsorb body fluids. Further information on those polymers is provided inEuropean Patent Application 773,315-A1, “Nonwoven Web Comprising WaterSoluble Polyamides and Articles Constructed Therefrom,” published May14, 1997 by S. U. Ahmed.

[0052] Useful polyampholytes include polyacrylamide-based copolymerswhich are highly sensitive to sodium chloride concentration.

[0053] U.S. Pat. No. 3,939,836, the disclosure of which is incorporatedherein by reference, describes an alkali salt of a sulfated celluloseester resin which gives good dry tensile strength to fabrics, whichstrength is retained in significant part when such fabrics are contactedwith a salt solution typical of body fluids such as blood, menstrualfluid or urine and yet are readily dispersible in water. The resins havea degree of sulfate substitution of from 0.10 to 0.45. In U.S. Pat. No.4,419,403, the disclosure of which is incorporated herein by reference,colloidal sulfate esters of cellulose are used for effectivewater-dispersible binders, wherein the binders have a much higher degreeof sulfate substitution than the '836 patent. The binders of the '403patent form gels in the presence of potassium ions. Other patentsrelated to dispersible polymers and wet wipes include U.S. Pat. Nos.4,117,187; 5,417,977; 4,309,469; 5,317,063; 5,312,883; 5,384,189;5,543,488; 5,571,876; 5,709,940; 5,718,790, the disclosures of which areincorporated herein by reference.

[0054] Co-Binder Polymers

[0055] As stated above, the polymer formulations of the presentinvention are formed from a single ion-sensitive polymer or acombination of two or more different polymers, wherein at least onepolymer is an ion-sensitive polymer. The second polymer may be aco-binder polymer. A co-binder polymer is of a type and in an amountsuch that when combined with the ion-sensitive polymer, the co-binderpolymer desirably is largely dispersed in the ion-sensitive polymer;i.e., the ion-sensitive polymer is desirably the continuous phase andthe co-binder polymer is desirably the discontinuous phase. Desirably,the co-binder polymer can also meet several additional criteria. Forexample, the co-binder polymer can have a glass transition temperature;i.e., T_(g), that is lower than the glass transition temperature of theion-sensitive polymer. Furthermore or alternatively, the co-binderpolymer can be insoluble in water, or can reduce the shear viscosity ofthe ion-sensitive polymer. The co-binder can be present at a levelrelative to the solids mass of the triggerable polymer of about 45% orless, specifically about 30% or less, more specifically about 20% orless, more specifically still about 15% or less, and most specificallyabout 10% or less, with exemplary ranges of from about 1% to about 45%or from about 25% to about 35%, as well as from about 1% to about 20% orfrom about 5% to about 25%. The amount of co-binder present should below enough, for co-binders with the potential to form water insolublebonds or films, that the co-binder remains a discontinuous phase unableto create enough crosslinked, or insoluble bonds, to jeopardize thedispersibility of the treated substrate. In one embodiment, theion-sensitive polymer formulation of the present invention can compriseabout 75 weight percent acrylic acid terpolymer and about 25 weightpercent poly(ethylene-vinyl acetate) co-binder.

[0056] Desirably, but not necessarily, the co-binder polymer whencombined with the ion-sensitive polymer will reduce the shear viscosityof the ion-sensitive polymer to such an extent that the combination ofthe ion-sensitive polymer and the co-binder polymer is sprayable. Bysprayable is mean that the polymer can be applied to a nonwoven fibroussubstrate by spraying and the distribution of the polymer across thesubstrate and the penetration of the polymer into the substrate are suchthat the polymer formulation is uniformly applied to the substrate.

[0057] The co-binder polymer can be in the form of an emulsion latex.The surfactant system used in such a latex emulsion should be such thatit does not substantially interfere with the dispersibility of theion-sensitive polymer.

[0058] In some embodiments, the combination of the ion-sensitive polymerand the co-binder polymer reduces the stiffness of the article to whichit is applied compared to the article with just the ion-sensitivepolymer. It has been found that when the ion-sensitive polymer, such asa sulfonate anion modified acrylic acid terpolymer, is applied to anonwoven substrate, such as an air laid layer of wood pulp, for thepurpose of forming a wet wipe, the nonwoven sheet can have anundesirable amount of stiffness that is detrimental to the dry productfeel or to the handling of the dry web during processing, when thebrittleness of the dry substrate can harm runnability. By combining theion-sensitive polymer and the co-binder polymer, the stiffness of sucharticles can be reduced.

[0059] The co-binder polymer of the present invention can have anaverage molecular weight, which varies depending on the ultimate use ofthe polymer. Desirably, the co-binder polymer has a weight averagemolecular weight ranging from about 500,000 to about 200,000,000. Moredesirably, the co-binder polymer has a weight average molecular weightranging from about 500,000 to about 100,000,000.

[0060] Co-binder polymers that can meet many or all of the foregoingcriteria include, but are not limited to, poly(ethylene-vinyl acetate),poly(styrene-butadiene), poly(styrene-acrylic), a vinyl acrylicterpolymer, neoprene, a polyester latex, an acrylic emulsion latex, polyvinyl chloride, ethylene-vinyl chloride copolymer, a carboxylated vinylacetate latex, and the like, all of which can be non-crosslinking (e.g.,devoid of N-methylol acrylamide or other crosslinkers), crosslinking, orpotentially crosslinking (i.e., prepared with a crosslinker present) butnot substantially crosslinked in the final product.

[0061] A particularly preferred non-crosslinking poly(ethylene-vinylacetate) is Dur-O-Set® RB available from National Starch and ChemicalCo., Bridgewater, N.J. A particularly preferred non-crosslinkingpoly(styrene-butadiene) is Rovene® 4817 available from Mallard CreekPolymers, Charlotte, N.C. A particularly preferred non-crosslinkingpoly(styrene-acrylic) is Rhoplex® NM 1715K available from Rohm and Haas,Philadelphia, Pa.

[0062] When a latex co-binder, or any potentially crosslinkableco-binder is used, the latex should be prevented from formingsubstantial water-insoluble bonds that bind the fibrous substratetogether and interfere with the dispersibility of the article. Thus, thelatex can be free of crosslinking agents, such as NMA, or free ofcatalyst for the crosslinker, or both. Alternatively, an inhibitor canbe added that interferes with the crosslinker or with the catalyst suchthat crosslinking is impaired even when the article is heated to normalcrosslinking temperatures. Such inhibitors can include free radicalscavengers, methyl hydroquinone, t-butylcatechol, pH control agents suchas potassium hydroxide, and the like. For some latex crosslinkers, suchas N-methylol-acrylamide (NMA), for example, elevated pH such as a pH of8 or higher can interfere with crosslinking at normal crosslinkingtemperatures (e.g., about 130° C. or higher). Also alternatively, anarticle comprising a latex co-binder can be maintained at temperaturesbelow the temperature range at which crosslinking takes place, such thatthe presence of a crosslinker does not lead to crosslinking, or suchthat the degree of crosslinking remains sufficiently low that thedispersibility of the article is not jeopardized. Also alternatively,the amount of crosslinkable latex can be kept below a threshold levelsuch that even with crosslinking, the article remains dispersible. Forexample, a small quantity of crosslinkable latex dispersed as discreteparticles in an ion-sensitive binder can permit dispersibility even whenfully crosslinked. For the later embodiment, the amount of latex can bebelow about 20 weight percent, and, more specifically, below about 15weight percent relative to the ion-sensitive binder.

[0063] Latex compounds, whether crosslinkable or not, need not be theco-binder. SEM micrography of successful ion-sensitive binder films withuseful non-crosslinking latex emulsions dispersed therein has shown thatthe latex co-binder particles can remain as discrete entities in theion-sensitive binder, possibly serving in part as filler material. It isbelieved that other materials could serve a similar role, including adispersed mineral or particulate filler in the ion-sensitive binder,optionally comprising added surfactants/dispersants. For example, in oneenvisioned embodiment, freeflowing Ganzpearl PS-8F particles fromPresperse, Inc. (Piscataway, N.J.), a styrene/divinylbenzene copolymerwith about 0.4 micron particles, can be dispersed in an ion-sensitivebinder at a level of about 2 to 10 weight percent to modify themechanical, tactile, and optical properties of the ion-sensitive binder.Other filler-like approaches could include microparticles, microspheres,or microbeads of metal, glass, carbon, mineral, quartz, and/or plastic,such as acrylic or phenolic, and hollow particles having inert gaseousatmospheres sealed within their interiors. Examples include EXPANCELphenolic microspheres from Expancel of Sweden, which expandsubstantially when heated, or the acrylic microspheres known as PM 6545available from PQ Corporation of Pennsylvania. Foaming agents, includingCO₂ dissolved in the ion-sensitive binder, could also provide helpfuldiscontinuities as gas bubbles in the matrix of an ion-sensitive binder,allowing the dispersed gas phase in the ion-sensitive binder to serve asthe co-binder. In general, any compatible material that is not misciblewith the binder, especially one with adhesive or binding properties ofits own, can be used as the co-binder, if it is not provided in a statethat imparts substantial covalent bonds joining fibers in a way thatinterferes with the water-dispersibility of the product. However, thosematerials that also provide additional benefits, such as reduced sprayviscosity, can be especially preferred. Adhesive co-binders, such aslatex that do not contain crosslinkers or contain reduced amounts ofcrosslinkers, have been found to be especially helpful in providing goodresults over a wide range of processing conditions, including drying atelevated temperatures.

[0064] As stated above, the T_(g) of the co-binder polymer can be lowerthan the T_(g) of the ion-sensitive polymer, which is believed toimprove the flexibility of the treated substrate, especially in the drystate. In Table 1 shown below is a comparison of the glass transitiontemperature of some of the preferred polymers useful in the presentinvention. TABLE 1 Glass Transition Temperatures For Select PolymersPolymer Glass Transition Temperature - Tg Sulfonate anion modifiedacrylic   55° C. acid terpolymer (dry) Sulfonate anion modified acrylic−22° C. acid terpolymer (wet) Rhoplex NW 1715K (dry)  −6° C. Rovene 4817(dry)  −4° C. Elite 33 (dry)   10° C. Elite 22 (dry) −15° C.

[0065] In an alternate embodiment, the ion-sensitive polymer formulationof the present invention comprises about 55 to about 95 weight percentsulfonate anion modified acrylic acid terpolymer and about 5 to about 45weight percent poly(ethylene-vinyl acetate). More desirably, theion-sensitive polymer formulation of the present invention comprisesabout 75 weight percent sulfonate anion modified acrylic acid terpolymerand about 25 weight percent poly(ethylene-vinyl acetate).

[0066] As stated above, useful co-binder polymers can include a varietyof commercial latex emulsions, including those selected from the Rovene®series (styrene butadiene latices available from Mallard Creek Polymersof Charlotte, N.C.), the Rhoplex® latices of Rohm and Haas Company, andthe Elite® latices of National Starch. Polymer emulsions or dispersionsgenerally comprise small polymer particles, such as crosslinkableethylene vinyl acetate copolymers, typically in spherical form,dispersed in water and stabilized with surface active ingredients suchas low molecular weight emulsifiers or high molecular weight protectivecolloids. These liquid binders can be applied to airlaid webs or othersubstrates by methods known in the art of binder treatment for nonwovenwebs, including spray or foam application, flooded nip impregnation,curtain coating, etc., followed by drying. In general, a wide variety oflatex compounds and other resins or emulsions can be considered,including vinyl acetate copolymer latices, such as 76 RES 7800 fromUnion Oil Chemicals Divisions and Resyn® 25-1103, Resyn® 25-1109, Resyn®25-1119, and Resyn® 25-1189 from National Starch and ChemicalCorporation, ethylene-vinyl acetate copolymer emulsions, such asAirflex® ethylene-vinylacetate from Air Products and Chemicals Inc.,acrylic-vinyl acetate copolymer emulsions, such as Rhoplex® AR-74 fromRohm and Haas Company, Synthemul® 97-726 from Reichhold Chemicals Inc.,Resyn® 25-1140, 25-1141, 25-1142, and Resyn-6820 from National Starchand Chemical Corporation, vinyl acrylic terpolymer latices, such as 76RES 3103 from Union Oil Chemical Division, and Resyn® 251110 fromNational Starch and Chemical Corporation, acrylic emulsion latices, suchas Rhoplex® B-15J, Rhoplex® P-376, Rhoplex® TR-407, Rhoplex® E-940,Rhoplex® TR934, Rhoplex® TR-520, Rhoplex® HA-24, and Rhoplex® NW1825from Rohm and Haas Company, and Hycar® 2600×322, Hycar® 2671, Hycar®2679, Hycar® 26120, and Hycar® 2600 X 347 from B. F. Goodrich ChemicalGroup, styrene-butadiene latices, such as 76 RES 4100 and 76 RES 8100available from Union Oil Chemicals Division, Tylac® resin emulsion68-412, Tylac® resin emulsion 68-067, 68-319, 68-413, 68-500, 68-501,available from Reichhold Chemical Inc., and DL6672A, DL6663A, DL6638A,DL6626A, DL6620A, DL615A, DL617A, DL620A, DL640A, DL650A available fromDow Chemical Company; and rubber latices, such as neoprene availablefrom Serva Biochemicals; polyester latices, such as Eastman AQ 29Davailable from Eastman Chemical Company; vinyl chloride latices, such asGeon® 352 from B. F. Goodrich Chemical Group; ethylene-vinyl chloridecopolymer emulsions, such as Airflex® ethylene-vinyl chloride from AirProducts and Chemicals; polyvinyl acetate homopolymer emulsions, such asVinac® from Air Products and Chemicals; carboxylated vinyl acetateemulsion resins, such as Synthemul® synthetic resin emulsions 40-502,40-503, and 97-664 from Reichhold Chemicals Inc. and Polyco® 2149, 2150,and 2171 from Rohm and Haas Company. Silicone emulsions and binders canalso be considered.

[0067] The co-binder polymer can comprise surface active compounds thatimprove the wettability of the substrate after application of the bindermixture.

[0068] Wettability of a dry substrate that has been treated with aion-sensitive polymer formulation can be a problem in some embodiments,because the hydrophobic portions of the ion-sensitive polymerformulation can become selectively oriented toward the air phase duringdrying, creating a hydrophobic surface that can be difficult to wet whenthe wetting composition is later applied unless surfactants are added tothe wetting composition. Surfactants, or other surface activeingredients, in co-binder polymers can improve the wettability of thedried substrate that has been treated with a ion-sensitive polymerformulation. Surfactants in the co-binder polymer should notsignificantly interfere with the ion-sensitive polymer formulation.Thus, the binder should maintain good integrity and tactile propertiesin the pre-moistened wipes with the surfactant present.

[0069] In one embodiment, an effective co-binder polymer replaces aportion of the ion-sensitive polymer formulation and permits a givenstrength level to be achieved in a pre-moistened wipe with at least oneof lower stiffness, better tactile properties (e.g., lubricity orsmoothness), or reduced cost, relative to an otherwise identicalpre-moistened wipe lacking the co-binder polymer and comprising theion-sensitive polymer formulation at a level sufficient to achieve thegiven tensile strength.

[0070] Other Co-Binder Polymers

[0071] The Dry Emulsion Powder (DEP) binders of Wacker Polymer Systems(Burghausen, Germany) such as the VINNEK® system of binders, can beapplied in some embodiments of the present invention. These areredispersible, free flowing binder powders formed from liquid emulsions.Small polymer particles from a dispersion are provided in a protectivematrix of water soluble protective colloids in the form of a powderparticle. The surface of the powder particle is protected against cakingby platelets of mineral crystals. As a result, polymer particles thatonce were in a liquid dispersion are now available in a free flowing,dry powder form that can be redispersed in water or turned into swollen,tacky particles by the addition of moisture. These particles can beapplied in highloft nonwovens by depositing them with the fibers duringthe airlaid process, and then later adding 10% to 30% moisture to causethe particles to swell and adhere to the fibers. This can be called the“chewing gum effect,” meaning that the dry, non-tacky fibers in the webbecome sticky like chewing gum once moistened. Good adhesion to polarsurfaces and other surfaces is obtained. These binders are available asfree flowing particles formed from latex emulsions that have been driedand treated with agents to prevent cohesion in the dry state. They canbe entrained in air and deposited with fibers during the airlaidprocess, or can be applied to a substrate by electrostatic means, bydirect contact, by gravity feed devices, and other means. They can beapplied apart from the binder, either before or after the binder hasbeen dried. Contact with moisture, either as liquid or steam, rehydratesthe latex particles and causes them to swell and to adhere to thefibers. Drying and heating to elevated temperatures (e.g., above 160°C.) causes the binder particles to become crosslinked and waterresistant, but drying at lower temperatures (e.g., at 110° C. or less)can result in film formation and a degree of fiber binding withoutseriously impairing the water dispersibility of the pre-moistened wipes.Thus, it is believed that the commercial product can be used withoutreducing the amount of crosslinker by controlling the curing of theco-binder polymer, such as limiting the time and temperature of dryingto provide a degree of bonding without significant crosslinking.

[0072] As pointed out by Dr. Klaus Kohlhammer in “New Airlaid Binders,”Nonwovens Report International, Sep. 1999, issue 342, pp. 20-22, 28-31,dry emulsion binder powders have the advantage that they can easily beincorporated into a nonwoven or airlaid web during formation of the web,as opposed to applying the material to an existing substrate, permittingincreased control over placement of the co-binder polymer. Thus, anonwoven or airlaid web can be prepared already having dry emulsionbinders therein, followed by moistening when the ion-sensitive polymerformulation solution is applied, whereupon the dry emulsion powderbecomes tacky and contributes to binding of the substrate.Alternatively, the dry emulsion powder can be entrapped in the substrateby a filtration mechanism after the substrate has been treated withion-sensitive binder and dried, whereupon the dry emulsion powder isrendered tacky upon application of the wetting composition.

[0073] In another embodiment, the dry emulsion powder is dispersed intothe ion-sensitive polymer formulation solution either by application ofthe powder as the ion-sensitive polymer formulation solution is beingsprayed onto the web or by adding and dispersing the dry emulsion powderparticles into the ion-sensitive polymer formulation solution, afterwhich the mixture is applied to a web by spraying, by foam applicationmethods, or by other techniques known in the art.

[0074] Binder Formulations and Fabrics Containing the Same

[0075] The polymer formulations of the present invention may be used asbinders. The binder formulations of the present invention may be appliedto any fibrous substrate. The binders are particularly suitable for usein water-dispersible products. Suitable fibrous substrates include, butare not limited to, nonwoven and woven fabrics. In many embodiments,particularly personal care products, preferred substrates are nonwovenfabrics. As used herein, the term “nonwoven fabric” refers to a fabricthat has a structure of individual fibers or filaments randomly arrangedin a mat-like fashion (including papers). Nonwoven fabrics can be madefrom a variety of processes including, but not limited to, air-laidprocesses, wet-laid processes, hydroentangling processes, staple fibercarding and bonding, and solution spinning.

[0076] The binder composition may be applied to the fibrous substrate byany known process of application. Suitable processes for applying thebinder material include, but are not limited to, printing, spraying,electrostatic spraying, coating, flooded nips, metered press rolls,impregnating or by any other technique. The amount of binder compositionmay be metered and distributed uniformly within the fibrous substrate ormay be non-uniformly distributed within the fibrous substrate. Thebinder composition may be distributed throughout the entire fibroussubstrate or it may be distributed within a multiplicity of smallclosely spaced areas. In most embodiments, uniform distribution ofbinder composition is desired.

[0077] For ease of application to the fibrous substrate, the binder maybe dissolved in water, or in a non-aqueous solvent such as methanol,ethanol, acetone, or the like, with water being the preferred solvent.The amount of binder dissolved in the solvent may vary depending on thepolymer used and the fabric application. Desirably, the binder solutioncontains up to about 25 percent by weight of binder composition solids.More desirably, the binder solution contains from about 10 to 20 percentby weight of binder composition solids, especially about 12 percent byweight binder composition solids. Plasticizers, perfumes, coloringagents, antifoams, bactericides, preservative, surface active agents,thickening agents, fillers, opacifiers, tackifiers, detackifiers, andsimilar additives can be incorporated into the solution of bindercomponents, if so desired.

[0078] Once the binder composition is applied to the substrate, thesubstrate is dried by any conventional means. Once dry, the coherentfibrous substrate exhibits improved tensile strength when compared tothe tensile strength of the untreated wet-laid or dry-laid substrates,and yet has the ability to rapidly “fall apart”, or disintegrate whenplaced in soft or hard water having a relatively high multivalent ionicconcentration and agitated. For example, the dry tensile strength of thefibrous substrate may be increased by at least 25 percent as compared tothe dry tensile strength of the untreated substrate not containing thebinder. More particularly, the dry tensile strength of the fibroussubstrate may be increase by at least 100 percent as compared to the drytensile strength of the untreated substrate not containing the binder.Even more particularly, the dry tensile strength of the fibroussubstrate may be increased by at least 500 percent as compared to thedry tensile strength of the untreated substrate not containing thebinder.

[0079] A desirable feature of the present invention is that theimprovement in tensile strength is effected where the amount of bindercomposition present, “add-on”, in the resultant fibrous substraterepresents only a small portion by weight of the entire substrate. Theamount of “add-on” can vary for a particular application; however, theoptimum amount of “add-on” results in a fibrous substrate which hasintegrity while in use and also quickly disperses when agitated inwater. For example, the binder components typically are from about 5 toabout 65 percent, by weight, of the total weight of the substrate. Moreparticularly, the binder components may be from about 10 to about 35percent, by weight, of the total weight of the substrate. Even moreparticularly, the binder components may be from about 17 to about 22percent by weight of the total weight of the substrate.

[0080] The nonwoven fabrics of the present invention have good in-usetensile strength, as well as, ion triggerability. Desirably, thenonwoven fabrics of the present invention are abrasion resistant andretain significant tensile strength in aqueous solutions containinggreater than about 0.3 weight percent NaCl, or a mixture of monovalentions, for those formulations using the acrylic acid terpolymer, andgreater than about 1 weight percent NaCl, or a mixture of monovalentions, for those formulations using the sulfonate anion modified acrylicacid terpolymer. Yet, the nonwoven fabrics are dispersible in very softto moderately hard to hard water. Because of this latter property,nonwoven fabrics of the present invention are well suited for disposableproducts, such as sanitary napkins, diapers, adult incontinenceproducts, and dry and premoistened wipes (wet wipes), which can bethrown in a flush toilet after use in any part of the world.

[0081] The fibers forming the fabrics above can be made from a varietyof materials including natural fibers, synthetic fibers, andcombinations thereof. The choice of fibers depends upon, for example,the intended end use of the finished fabric and fiber cost. Forinstance, suitable fibrous substrates may include, but are not limitedto, natural fibers such as cotton, linen, jute, hemp, wool, wood pulp,etc. Similarly, regenerated cellulosic fibers, such as viscose rayon andcuprammonium rayon, modified cellulosic fibers, such as celluloseacetate, or synthetic fibers, such as those derived from polypropylenes,polyethylenes, polyolefins, polyesters, polyamides, polyacrylics, etc.,alone or in combination with one another, may likewise be used. Blendsof one or more of the above fibers may also be used, if so desired.Among wood pulp fibers, any known papermaking fibers may be used,including softwood and hardwood fibers. Fibers, for example, may bechemically pulped or mechanically pulped, bleached or unbleached, virginor recycled, high yield or low yield, and the like. Mercerized,chemically stiffened or crosslinked fibers may also be used.

[0082] Synthetic cellulose fiber types include rayon in all itsvarieties and other fibers derived from viscose or chemically modifiedcellulose, including regenerated cellulose and solvent-spun cellulose,such as Lyocell. Chemically treated natural cellulosic fibers can beused, such as mercerized pulps, chemically stiffened or crosslinkedfibers, or sulfonated fibers. Recycled fibers, as well as virgin fibers,can be used. Cellulose produced by microbes and other cellulosicderivatives can be used. As used herein, the term “cellulosic” is meantto include any material having cellulose as a major constituent, and,specifically, comprising at least 50 percent by weight cellulose or acellulose derivative. Thus, the term includes cotton, typical woodpulps, non-woody cellulosic fibers, cellulose acetate, cellulosetriacetate, rayon, thermomechanical wood pulp, chemical wood pulp,debonded chemical wood pulp, milkweed, or bacterial cellulose. The fiberlength is important in producing the fabrics of the present invention.In some embodiments, such as flushable products, fiber length is of moreimportance. The minimum length of the fibers depends on the methodselected for forming the fibrous substrate. For example, where thefibrous substrate is formed by carding, the length of the fiber shouldusually be at least about 42 mm in order to insure uniformity. Where thefibrous substrate is formed by air-laid or wet-laid processes, the fiberlength may desirably be about 0.2 to 6 mm. Although fibers having alength of greater than 50 mm are within the scope of the presentinvention, it has been determined that when a substantial quantity offibers having a length greater than about 15 mm is placed in a flushablefabric, though the fibers will disperse and separate in water, theirlength tends to form “ropes” of fibers, which are undesirable whenflushing in home toilets. Therefore, for these products, it is desiredthat the fiber length be about 15 mm or less so that the fibers will nothave a tendency to “rope” when they are flushed through a toilet.Although fibers of various lengths are applicable in the presentinvention, desirably fibers are of a length less than about 15 mm sothat the fibers disperse easily from one another when in contact withwater. The fibers, particularly synthetic fibers, can also be crimped.

[0083] The fabrics of the present invention may be formed from a singlelayer or multiple layers. In the case of multiple layers, the layers aregenerally positioned in a juxtaposed or surface-to-surface relationshipand all or a portion of the layers may be bound to adjacent layers.Nonwoven webs of the present invention may also be formed from aplurality of separate nonwoven webs wherein the separate nonwoven websmay be formed from single or multiple layers. In those instances wherethe nonwoven web includes multiple layers, the entire thickness of thenonwoven web may be subjected to a binder application or each individuallayer may be separately subjected to a binder application and thencombined with other layers in a juxtaposed relationship to form thefinished nonwoven web.

[0084] In one embodiment, the fabric substrates of the present inventionmay be incorporated into cleansing and body fluid absorbent products,such as sanitary napkins, diapers, adult incontinence products, surgicaldressings, tissues, wet wipes, and the like. These products may includean absorbent core, comprising one or more layers of an absorbent fibrousmaterial. The core may also comprise one or more layers of afluid-pervious element, such as fibrous tissue, gauze, plastic netting,etc. These are generally useful as wrapping materials to hold thecomponents of the core together. Additionally, the core may comprise afluid-impervious element or barrier means to preclude the passage offluid through the core and on the outer surfaces of the product.Desirably, the barrier means also is water-dispersible. A film of apolymer having substantially the same composition as the aforesaidwater-dispersible binder is particularly well-suited for this purpose.In accordance with the present invention, the polymer compositions areuseful for forming each of the above-mentioned product componentsincluding the layers of absorbent core, the fluid-pervious element, thewrapping materials, and the fluid-impervious element or barrier means.

[0085] The binder formulations of the present invention are particularlyuseful for binding fibers of air-laid nonwoven fabrics. These air-laidmaterials are useful for body-side liners, fluid distribution materials,fluid in-take materials, such as a surge material, absorbent wrap sheetand cover stock for various water-dispersible personal care products.Air-laid materials are particularly useful for use as a pre-moistenedwipe (wet wipe). The basis weights for air-laid non-woven fabrics mayrange from about 20 to about 200 grams per square meter (“gsm”) withstaple fibers having a denier of about 0.5-10 and a length of about 6-15millimeters. Surge, or in-take, materials need better resiliency andhigher loft so staple fibers having about 6 denier or greater are usedto make these products. A desirable final density for the surge, orin-take, materials is between about 0.025 grams per cubic centimeter(“g/cc”) to about 0.10 g/cc. Fluid distribution materials may have ahigher density, in the desired range of about 0.10 to about 0.20 g/ccusing fibers of lower denier, most desirable fibers have a denier ofless than about 1.5. Wipes generally can have a fiber density of about0.025 g/cc to about 0.2 g/cc and a basis weight of about 20 gsm to about150 gsm; specifically from about 30 to about 90 gsm, and mostspecifically from about 60 gsm to about 65 gsm. The wipe retains itsstructure, softness and exhibits a toughness satisfactory for practicaluse. However, when brought into contact with water having aconcentration of multivalent ions, such as Ca²⁺ and Mg²⁺ ions, of up toabout 200 ppm, the wipe disperses. Similarly, when brought into contactwith water having a concentration of multivalent ions, such as Ca²⁺ andMg²⁺ ions, of less than about 10 ppm, the wipe disperses. The wipe isthen easily broken into fibers and/or small pieces and dispersed in thewater.

[0086] The nonwoven fabrics of the present invention may also beincorporated into such body fluid absorbing products as sanitarynapkins, diapers, surgical dressings, tissues and the like. In oneembodiment, the binder is such that it will not dissolve when contactedby body fluids since the concentration of monovalent ions in the bodyfluids is above the level needed for dissolution; i.e., greater that0.3% by weight and/or greater than 1% by weight. The nonwoven fabricretains its structure, softness and exhibits a toughness satisfactoryfor practical use. However, when brought into contact with water havinga concentration of multivalent ions, such as Ca²⁺ and Mg²⁺ ions, of upto about 200 ppm, the binder, such as one comprising a sulfonate anionmodified acrylic acid terpolymer, disperses. Similarly, when broughtinto contact with water having a concentration of multivalent ions, suchas Ca²⁺ and Mg²⁺ ions, of less than about 10 ppm, the binder comprisingthe acrylic acid terpolymer disperses. The nonwoven fabric structure isthen easily dispersed in the water.

[0087] In one embodiment of the present invention, the in-use tensilestrength of a nonwoven fabric is enhanced by forming the nonwoven fabricwith a binder material comprising an ion-sensitive polymer formulationof the present invention and subsequently applying one or moremonovalent and/or multivalent salts to the nonwoven fabric. The salt maybe applied to the nonwoven fabric by any method known to those ofordinary skill in the art including, but not limited to, applying asolid powder onto the fabric and spraying a salt solution onto thefabric. The amount of salt may vary depending on a particularapplication. However, the amount of salt applied to the fabric istypically from about 0.1 weight percent to about 10 weight percent saltsolids based on the total weight of the fabric. The salt-containingfabrics of the present invention may be used in a variety of fabricapplications including, but not limited to, feminine pads, surgicaldressings, and diapers.

[0088] Those skilled in the art will readily understand that the binderformulations and fibrous substrates of the present invention may beadvantageously employed in the preparation of a wide variety ofproducts, including but not limited to, absorbent personal care productsdesigned to be contacted with body fluids. Such products may onlycomprise a single layer of the fibrous substrate, or may comprise acombination of elements, as described above. Although the binderformulations and fibrous substrates of the present invention areparticularly suited for personal care products, the binder formulationsand fibrous substrates may be advantageously employed in a wide varietyof consumer products.

[0089] The combination of the acrylic acid terpolymer or the sulfonateanion modified acrylic acid terpolymer and the non-crosslinkingpoly(ethylene-vinyl acetate) of the present invention produces improvedresults over the use of the terpolymer alone. For example, when theion-sensitive polymer formulation of the present invention is used for abinder composition for wet wipes, the wet wipes have improvedwettability on first insult without losing dispersibility which allowsthe wipe basesheet to wet out easily with the wet wipe solution atcommercial speeds. The ion-sensitive polymer formulation of the presentinvention also can reduce the stiffness of the dry basesheet, improvethe runnability of the dry and otherwise brittle sheet during furtherconversion of the product, reduce the stickiness of the wipes and/orimprove the sprayability of the ion-sensitive binder, thereby improvingbinder distribution and penetration in the basesheet.

[0090] Unlike other binder systems known in the art, the ion-sensitivepolymer formulations of the present invention can be activated asbinders without the need for elevated temperature. While drying or waterremoval is useful in achieving a good distribution of the binder in afibrous web, elevated temperature, per se, is not essential because thebinder does not require crosslinking or other chemical reactions withhigh activation energy to serve as a binder. Rather, the interactionwith a soluble activating compound, typically a salt, is sufficient tocause the binder to become active (insoluble) or “salted out.” Thus, adrying step can be avoided, if desired, or replaced with low-temperaturewater removal operations such as room-temperature drying or freezedrying. Elevated temperature is generally helpful for drying, but thedrying can be done at temperatures below what is normally needed todrive crosslinking reactions. Thus, the peak temperature to which thesubstrate is exposed or to which the substrate is brought can be belowany of the following: 180° C., 160° C., 140° C., 120° C., 110° C., 105°C., 1000 C., 90° C., 75° C., and 60° C., with an exemplary range forpeak web temperature of from about 50° C. to about 110° C., or fromabout 70° C. to about 140° C. Of course, higher temperatures can beused, but are not necessary in most embodiments. While co-binder polymersystems, such as commercial latex emulsions, may also comprisecrosslinkers suited for reaction at temperatures of 160° C. or higher,maintaining a lower peak temperature can be beneficial in preventingdevelopment of excessive strength in the co-binder polymer that mightotherwise hinder the water dispersibility of the pre-moistened wipe.

[0091] Wet Wipe Wetting Composition and Wet Wipes Containing the Same

[0092] One particularly interesting embodiment of the present inventionis the production of pre-moistened wipes, or wet wipes, from theabove-described ion-sensitive binder compositions and fibrous materials.For wipes, the fibrous material may be in the form of a woven ornonwoven fabric; however, nonwoven fabrics are more desirable. Thenonwoven fabric is, desirably, formed from relatively short fibers, suchas wood pulp fibers. The minimum length of the fibers depends on themethod selected for forming the nonwoven fabric. Where the nonwovenfabric is formed by a wet or dry method, the fiber length is desirablyfrom about 0.1 millimeters to about 15 millimeters. Desirably, thenonwoven fabric of the present invention has a relatively low wetcohesive strength when it is not bonded together by an adhesive orbinder material. When such nonwoven fabrics are bonded together by abinder composition, which loses its bonding strength in tap water and insewer water, the fabric will break up into fibers and/or small piecesreadily by the agitation provided by flushing and moving through thesewer pipes.

[0093] The finished wipes may be individually packaged, desirably in afolded condition, in a moisture proof envelope or packaged in containersholding any desired number of sheets in a water-tight package with awetting composition applied to the wipe. The finished wipes may also bepackaged as a roll of separable sheets in a moisture-proof containerholding any desired number of sheets on the roll with a wettingcomposition applied to the wipes. The roll can be coreless and eitherhollow or solid. Coreless rolls, including rolls with a hollow center orwithout a solid center, can be produced with known coreless rollwinders, including those of SRP Industry, Inc. (San Jose, Calif.);Shimizu Manufacturing (Japan), and the devices disclosed in U.S. Pat.No. 4,667,890, issued May 26, 1987 to Gietman. Solid-wound corelessrolls can offer more product for a given volume and can be adapted for awide variety of dispensers.

[0094] Relative to the weight of the dry fabric, the wipe may desirablycontain from about 10 percent to about 400 percent of the wettingcomposition, more desirably from about 100 percent to about 300 percentof the wetting composition, and even more desirably from about 180percent to about 240 percent of the wetting composition. The wipemaintains its desired characteristics over the time periods involved inwarehousing, transportation, retail display and storage by the consumer.Accordingly, shelf life may range from two months to two years.

[0095] Various forms of impermeable envelopes and storage means forcontaining wet-packaged materials such as wipes and towelettes and thelike are well known in the art. Any of these may be employed inpackaging the pre-moistened wipes of the present invention.

[0096] Desirably, the pre-moistened wipes of the present invention arewetted with an aqueous wetting composition, which has one or more of thefollowing properties:

[0097] (1) is compatible with the above-described ion-sensitive bindercompositions of the present invention;

[0098] (2) enables the pre-moistened wipe to maintain its wet strengthduring converting, storage and usage (including dispensing), as well as,dispersibility in a toilet bowl;

[0099] (3) does not cause skin irritation and is safe to use on skin;

[0100] (4) reduces tackiness of the wipe, and provides unique tactileproperties, such as skin glide and a “lotion-like feel”; and

[0101] (5) acts as a vehicle to deliver “moist cleansing” and other skinhealth benefits.

[0102] As set forth previously, unlike the prior art, the wet wipes ofthe present invention do not need organic solvents to maintain in-usewet strength, though organic solvents may be included for differentpurposes other than maintaining in-use wet strength. The organicsolvents may produce a greasy after-feel and cause irritation in higheramounts. As such, the wetting composition desirably does not act as asolvent for the binder and generally does not contain solvents otherthan water, and particularly does not contain organic solvents toprovide wet strength. However, a small quantity (less than about 1%) ofa fragrance solubilizer such as polysorbate 20 may be present, dependingon the fragrance and the salt concentration of the wetting composition.If organic solvents are used, lower amounts are desired. As such, thewetting composition desirably contains less than about 5 weight percentof organic solvents, such as propylene glycol or other glycols,polyhydroxy alcohols, and the like, based on the total weight of thewetting composition. More desirably, the wetting composition containsless than about 3 weight percent of organic solvents. Even moredesirably, the wetting composition contains less than about 1 weightpercent of organic solvents. The wetting composition can besubstantially free of organic solvents.

[0103] One aspect of the present invention is a wetting composition,which contains an activating compound that maintains the strength of awater-dispersible binder until the activating compound is diluted withwater, whereupon the strength of the water-dispersible binder begins todecay. The water-dispersible binder may be any of the ion-sensitivebinder compositions of the present invention or any other ion-sensitivebinder composition. The activating compound in the wetting compositioncan be a salt, such as sodium chloride, or any other compound, whichprovides in-use and storage strength to the water-dispersible bindercomposition, and can be diluted in water to permit dispersion of thesubstrate as the binder polymer triggers to a weaker state. Desirably,the wetting composition contains less than about 10 weight percent of anactivating compound based on the total weight of the wettingcomposition. Specifically, the wetting composition may contain fromabout 0.3 weight percent to about 5 weight percent of an activatingcompound. Even more specifically, the wetting composition may containfrom about 2 weight percent to about 4 weight percent of an activatingcompound.

[0104] The wetting composition of the present invention may furthercomprise a variety of additives compatible with the activating compoundand the water-dispersible binder, such that the strength anddispersibility functions of the wipe are not jeopardized. Suitableadditives in the wetting composition include, but are not limited to,the following additives: skin-care additives; odor control agents;detackifying agents to reduce the tackiness of the binder; particulates;antimicrobial agents; preservatives; wetting agents and cleaning agentssuch as detergents, surfactants, and some silicones; emollients; surfacefeel modifiers for improved tactile sensation (e.g., lubricity) on theskin; fragrance; fragrance solubilizers; opacifiers; fluorescentwhitening agents; UV absorbers; pharmaceuticals; and pH control agents,such as malic acid or potassium hydroxide.

[0105] Skin-Care Additives

[0106] As used herein, the term “skin-care additives” representsadditives, which provide one or more benefits to the user, such as areduction in the probability of having diaper rash and/or other skindamage caused by fecal enzymes. These enzymes, particularly trypsin,chymotrypsin and elastase, are proteolytic enzymes produced in thegastrointestinal tract to digest food. In infants, for example, thefeces tend to be watery and contain, among other materials, bacteria,and some amounts of undegraded digestive enzymes. These enzymes, if theyremain in contact with the skin for any appreciable period of time, havebeen found to cause an irritation that is uncomfortable in itself andcan predispose the skin to infection by microorganisms. As acountermeasure, skin-care additives include, but are not limited to, theenzyme inhibitors and sequestrants set forth hereafter. The wettingcomposition may contain less than about 5 weight percent of skin-careadditives based on the total weight of the wetting composition. Morespecifically, the wetting composition may contain from about 0.01 weightpercent to about 2 weight percent of skin-care additives. Even morespecifically, the wetting composition may contain from about 0.01 weightpercent to about 0.05 weight percent of skin-care additives.

[0107] A variety of skin-care additives may be added to the wettingcomposition and the pre-moistened wipes of the present invention orincluded therein. In one embodiment of the present invention, skin-careadditives in the form of particles are added to serve as fecal enzymeinhibitors, offering potential benefits in the reduction of diaper rashand skin damage caused by fecal enzymes. U.S. Pat. No. 6,051,749, issuedApr. 18, 2000 to Schulz et al., the entirety of which is hereinincorporated by reference, discloses organophilic clays in a woven ornonwoven web, said to be useful for inhibiting fecal enzymes. Suchmaterials may be used in the present invention, including reactionproducts of a long chain organic quaternary ammonium compound with oneor more of the following clays: montmorillonite, bentonite, beidellite,hectorite, saponite, and stevensite.

[0108] Other known enzyme inhibitors and sequestrants may be used asskin-care additives in the wetting composition of the present invention,including those that inhibit trypsin and other digestive or fecalenzymes, and inhibitors for urease. For example, enzyme inhibitors andanti-microbial agents may be used to prevent the formation of odors inbody fluids. For example, urease inhibitors, which are also said to playa role in odor absorption, are disclosed by T. Trinh in World PatentApplication No. 98/26808, “Absorbent Articles with Odor Control System,”published Jun. 25, 1998, the entirety of which is herein incorporated byreference. Such inhibitors may be incorporated into the wettingcomposition and the pre-moistened wipes of the present invention andinclude transition metal ions and their soluble salts, such as silver,copper, zinc, ferric, and aluminum salts. The anion may also provideurease inhibition, such as borate, phytate, etc. Compounds of potentialvalue include, but are not limited to, silver chlorate, silver nitrate,mercury acetate, mercury chloride, mercury nitrate, copper metaborate,copper bromate, copper bromide, copper chloride, copper dichromate,copper nitrate, copper salicylate, copper sulfate, zinc acetate, zincborate, zinc phytate, zinc bromate, zinc bromide, zinc chlorate, zincchloride, zinc sulfate, cadmium acetate, cadmium borate, cadmiumbromide, cadmium chlorate, cadmium chloride, cadmium formate, cadmiumiodate, cadmium iodide, cadmium permanganate, cadmium nitrate, cadmiumsulfate, and gold chloride.

[0109] Other salts that have been disclosed as having urease inhibitionproperties include ferric and aluminum salts, especially the nitrates,and bismuth salts. Other urease inhibitors are disclosed by Trinh,including hydroxamic acid and its derivatives; thiourea; hydroxylamine;salts of phytic acid; extracts of plants of various species, includingvarious tannins, e.g. carob tannin, and their derivatives such aschlorogenic acid derivatives; naturally occurring acids such as ascorbicacid, citric acid, and their salts; phenyl phosphoro diamidate/diaminophosphoric acid phenyl ester; metal aryl phosphoramidate complexes,including substituted phosphorodiamidate compounds; phosphoramidateswithout substitution on the nitrogen; boric acid and/or its salts,including especially, borax, and/or organic boron acid compounds; thecompounds disclosed in European Patent Application 408,199; sodium,copper, manganese, and/or zinc dithiocarbamate; quinones; phenols;thiurams; substituted rhodanine acetic acids; alkylated benzoquinones;formamidine disulphide; 1:3-diketones maleic anhydride; succinamide;phthalic anhydride; pehenic acid; /N,N-dihalo-2-imidazolidinones;N-halo2-oxazolidinones; thio- and/or acyl-phosphoryltnamide and/orsubstituted derivatives thereof-, thiopyridine-N-oxides, thiopyridines,and thiopyrimidines; oxidized sulfur derivatives of diarninophosphinylcompounds; cyclotriphosphazatriene derivatives; ortho-diaminophosphinylderivatives of oximes; bromo-nitro compounds; S-aryl and/or alkyldiamidophosphorothiolates; diaminophosphinyl derivatives; mono- and/orpolyphosphorodiamide; 5-substituted-benzoxathiol-2-ones;N(diaminophosphinyl)arylcarboxamides; alkoxy-1,2-benzothaizin compounds;etc.

[0110] Many other skin-care additives may be incorporated into thewetting composition and pre-moistened wipes of the present invention,including, but not limited to, sun blocking agents and UV absorbers,acne treatments, pharmaceuticals, baking soda (including encapsulatedforms thereof), vitamins and their derivatives such as Vitamins A or E,botanicals such as witch hazel extract and aloe vera, allantoin,emollients, disinfectants, hydroxy acids for wrinkle control oranti-aging effects, sunscreens, tanning promoters, skin lighteners,deodorants and anti-perspirants, ceramides for skin benefits and otheruses, astringents, moisturizers, nail polish removers, insectrepellants, antioxidants, antiseptics, anti-inflammatory agents and thelike, provided that the additives are compatible with an ion-sensitivebinder composition associated therewith, and especially theion-sensitive binder compositions of the present invention (i.e., theydo not cause a substantial loss of strength in the wet state of thepre-moistened wipes, prior to dilution in water, while permittingdispersibility in water).

[0111] Useful materials for skin care and other benefits are listed inMcCutcheon's 1999, Vol. 2: Functional Materials, MC Publishing Company,Glen Rock, NJ. Many useful botanicals for skin care are provided byActive Organics, Lewisville, Tex.

[0112] Odor Control Additives

[0113] Suitable odor control additives for use in the wettingcomposition and pre-moistened wipes of the present invention include,but are not limited to, zinc salts; talc powder; encapsulated perfumes(including microcapsules, macrocapsules, and perfume encapsulated inliposomes, vessicles, or microemulsions); chelants, such asethylenediamine tetra-acetic acid; zeolites; activated silica, activatedcarbon granules or fibers; activated silica particulates; polycarboxylicacids, such as citric acid; cyclodextrins and cyclodextrin derivatives;chitosan or chitin and derivatives thereof; oxidizing agents;antimicrobial agents, including silver-loaded zeolites (e.g., those ofBF Technologies, located in Beverly, Massachusetts, sold under thetrademark HEALTHSHIELD™); triclosan; kieselguhr; and mixtures thereof.In addition to controlling odor from the body or body wastes, odorcontrol strategies can also be employed to mask or control any odor ofthe treated substrate. Desirably, the wetting composition contains lessthan about 5 weight percent of odor control additives based on the totalweight of the wetting composition. More desirably, the wettingcomposition contains from about 0.01 weight percent to about 2 weightpercent of odor control additives. Even more desirably, the wettingcomposition contains from about 0.03 weight percent to about 1 weightpercent of odor control additives.

[0114] In one embodiment of the present invention, the wettingcomposition and/or pre-moistened wipes comprise derivatizedcyclodextrins, such as hydroxypropyl beta-cyclodextrin in solution,which remain on the skin after wiping and provide an odor-absorbinglayer. In other embodiments, the odor source is removed or neutralizedby application of an odor-control additive, exemplified by the action ofa chelant that binds metal groups necessary for the function of manyproteases and other enzymes that commonly produce an odor. Chelating themetal group interferes with the enzyme's action and decreases the riskof malodor in the product.

[0115] Principles for the application of chitosan or chitin derivativesto nonwoven webs and cellulosic fibers are described by S. Lee et al. in“Antimicrobial and Blood Repellent Finishes for Cotton and NonwovenFabrics Based on Chitosan and Fluoropolymers,” Textile Research Journal,69(2); 104-112, February 1999.

[0116] Detackifying Agents

[0117] While elevated salt concentrations may reduce the tack of theion-sensitive binder, other means of tack reduction are often desirable.Thus, detackifying agents may be used in the wetting composition toreduce the tackiness, if any, of the ion-sensitive binder. Suitabledetackifiers include any substance known in the art to reduce tackbetween two adjacent fibrous sheets treated with an adhesive-likepolymer or any substance capable of reducing the tacky feel of anadhesive-like polymer on the skin. Detackifiers may be applied as solidparticles in dry form, as a suspension or as a slurry of particles.Deposition may be by spray, coating, electrostatic deposition,impingement, filtration (i.e., a pressure differential drives aparticle-laden gas phase through the substrate, depositing particles bya filtration mechanism), and the like, and may be applied uniformly onone or more surfaces of the substrate or may be applied in a pattern(e.g., repeating or random patterns) over a portion of the surface orsurfaces of the substrate. The detackifier may be present throughout thethickness of the substrate, but may be concentrated at one or bothsurfaces, and may be substantially only present on one or both surfacesof the substrate.

[0118] Specific detackifiers include, but are not limited to, powders,such as talc powder, calcium carbonate, mica; starches, such as cornstarch; lycopodium powder; mineral fillers, such as titanium dioxide;silica powder; alumina; metal oxides in general; baking powder;kieselguhr; and the like. Polymers and other additives having lowsurface energy may also be used, including a wide variety of fluorinatedpolymers, silicone additives, polyolefins and thermoplastics, waxes,debonding agents known in the paper industry including compounds havingalkyl side chains such as those having 16 or more carbons, and the like.Compounds used as release agents for molds and candle making may also beconsidered, as well as, dry lubricants and fluorinated release agents.

[0119] In one embodiment, the detackifier comprisespolytetrafluorethylene (PTFE), such as PTFE telomer (KRYTOX® DF)compound, used in the PTFE release agent dry lubricant MS-122DF,marketed by Miller-Stephenson (Danbury, Conn.) as a spray product. Forexample, PTFE particles may be applied by spray to one side of thesubstrate prior to winding of the pre-moistened wipes. In oneembodiment, a detackifying agent is applied to only one surface of thesubstrate prior to winding into a roll.

[0120] The wetting composition desirably contains less than about 25weight percent of detackifying agents based on the total weight of thewetting composition. More desirably, the wetting composition containsfrom about 0.01 weight percent to about 10 weight percent ofdetackifying agents, more specifically about 5% or less. Even morespecifically, the wetting composition contains from about 0.05 weightpercent to about 2 weight percent of detackifying agents.

[0121] In addition to acting as a detackifying agent, starch compoundsmay also improve the strength properties of the pre-moistened wipes. Forexample, it has been found that ungelled starch particles, such ashydrophilic tapioca starch, when present at a level of about 1% orhigher by weight relative to the weight of the wetting composition, canpermit the pre-moistened wipe to maintain the same strength at a lowersalt concentration than is possible without the presence of starch.Thus, for example, a given strength can be achieved with about 2% saltin the wetting composition in the presence of salt compared to a levelof about 4% salt being needed without starch. Starch may be applied byadding the starch to a suspension of laponite to improve the dispersionof the starch within the wetting composition.

[0122] Microparticulates

[0123] The wetting composition of the present invention may be furthermodified by the addition of solid particulates or microparticulates.Suitable particulates include, but are not limited to, mica, silica,alumina, calcium carbonate, kaolin, talc, and zeolites. The particulatesmay be treated with stearic acid or other additives to enhance theattraction or bridging of the particulates to the binder system, ifdesired. Also, two-component microparticulate systems, commonly used asretention aids in the papermaking industry, may also be used. Suchtwo-component microparticulate systems generally comprise a colloidalparticle phase, such as silica particles, and a water-soluble cationicpolymer for bridging the particles to the fibers of the web to beformed. The presence of particulates in the wetting composition canserve one or more useful functions, such as (1) increasing the opacityof the pre-moistened wipes; (2) modifying the rheology or reducing thetackiness of the pre-moistened wipe; (3) improving the tactileproperties of the wipe; or (4) delivering desired agents to the skin viaa particulate carrier, such as a porous carrier or a microcapsule.Desirably, the wetting composition contains less than about 25 weightpercent of particulate based on the total weight of the wettingcomposition. More specifically, the wetting composition may contain fromabout 0.05 weight percent to about 10 weight percent ofmicroparticulate. Even more specifically, the wetting composition maycontain from about 0.1 weight percent to about 5 weight percent ofmicroparticulate.

[0124] Microcapsules and Other Delivery Vehicles

[0125] Microcapsules and other delivery vehicles may also be used in thewetting composition of the present invention to provide skin-careagents; medications; comfort promoting agents, such as eucalyptus;perfumes; skin care agents; odor control additives; vitamins; powders;and other additives to the skin of the user. Specifically, the wettingcomposition may contain up to about 25 weight percent of microcapsulesor other delivery vehicles based on the total weight of the wettingcomposition. More specifically, the wetting composition may contain fromabout 0.05 weight percent to about 10 weight percent of microcapsules orother delivery vehicles. Even more specifically, the wetting compositionmay contain from about 0.2 weight percent to about 5.0 weight percent ofmicrocapsules or other delivery vehicles.

[0126] Microcapsules and other delivery vehicles are well known in theart. For example, POLY-PORE® E200 (Chemdal Corp., Arlington Heights,Ill.), is a delivery agent comprising soft, hollow spheres that cancontain an additive at over 10 times the weight of the delivery vehicle.Known additives reported to have been used with POLY-PORE® E200 include,but are not limited to, benzoyl peroxide, salicylic acid, retinol,retinyl palmitate, octyl methoxycinnamate, tocopherol, siliconecompounds (DC 435), and mineral oil. Another useful delivery vehicle isa sponge-like material marketed as POLY-PORE® L200, which is reported tohave been used with silicone (DC₄₃₅) and mineral oil. Other knowndelivery systems include cyclodextrins and their derivatives, liposomes,polymeric sponges, and spray-dried starch.

[0127] Additives present in microcapsules are isolated from theenvironment and the other agents in the wetting composition until thewipe is applied to the skin, whereupon the microcapsules break anddeliver their load to the skin or other surfaces.

[0128] Preservatives and Anti-Microbial Agents

[0129] The wetting composition of the present invention may also containpreservatives and/or anti-microbial agents. Several preservatives and/oranti-microbial agents, such as Mackstat H 66 (available from McIntyreGroup, Chicago, Ill.), have been found to give excellent results inpreventing bacteria and mold growth. Other suitable preservatives andanti-microbial agents include, but are not limited to DMDM hydantoin(e.g., Glydant PIus™, Lonza, Inc., Fair Lawn, N.J.), iodopropynylbutylcarbamate, Kathon (Rohm and Hass, Philadelphia, Pa.),methylparaben, propylparaben, 2-bromo-2-nitropropane-1,3-diol, benzoicacid, and the like. Desirably, the wetting composition contains lessthan about 2 weight percent on an active basis of preservatives and/oranti-microbial agents based on the total weight of the wettingcomposition. More desirably, the wetting composition contains from about0.01 weight percent to about 1 weight percent of preservatives and/oranti-microbial agents. Even more desirably, the wetting compositioncontains from about 0.01 weight percent to about 0.5 weight percent ofpreservatives and/or anti-microbial agents.

[0130] Wetting Agents and Cleaning Agents

[0131] A variety of wetting agents and/or cleaning agents may be used inthe wetting composition of the present invention. Suitable wettingagents and/or cleaning agents include, but are not limited to,detergents and nonionic, amphoteric, and anionic surfactants, especiallyamino acid-based surfactants. Amino acid-based surfactant systems, suchas those derived from amino acids L-glutamic acid and other naturalfatty acids, offer pH compatibility to human skin and good cleansingpower, while being relatively safe and providing improved tactile andmoisturization properties compared to other anionic surfactants. Onefunction of the surfactant is to improve wetting of the dry substratewith the wetting composition. Another function of the surfactant can beto disperse bathroom soils when the pre-moistened wipe contacts a soiledarea and to enhance their absorption into the substrate. The surfactantcan further assist in make-up removal, general personal cleansing, hardsurface cleansing, odor control, and the like.

[0132] One commercial example of an amino-acid based surfactant isacylglutamate, marketed under the Amisoft name by Ajinomoto Corp.,Tokyo, Japan. Desirably, the wetting composition contains less thanabout 3 weight percent of wetting agents and/or cleaning agents based onthe total weight of the wetting composition. More desirably, the wettingcomposition contains from about 0.01 weight percent to about 2 weightpercent of wetting agents and/or cleaning agents. Even more desirably,the wetting composition contains from about 0.1 weight percent to about0.5 weight percent of wetting agents and/or cleaning agents.

[0133] Although amino-acid based surfactant are particularly useful inthe wetting compositions of the present invention, a wide variety ofsurfactants may be used in the present invention. Suitable non-ionicsurfactants include, but are not limited to, the condensation productsof ethylene oxide with a hydrophobic (oleophilic) polyoxyalkylene baseformed by the condensation of propylene oxide with propylene glycol. Thehydrophobic portion of these compounds desirably has a molecular weightsufficiently high so as to render it water-insoluble. The addition ofpolyoxyethylene moieties to this hydrophobic portion increases thewater-solubility of the molecule as a whole, and the liquid character ofthe product is retained up to the point where the polyoxyethylenecontent is about 50% of the total weight of the condensation product.Examples of compounds of this type include commercially-availablePluronic surfactants (BASF Wyandotte Corp.), especially those in whichthe polyoxypropylene ether has a molecular weight of about 1500-3000 andthe polyoxyethylene content is about 35-55% of the molecule by weight,i.e. Pluronic L-62.

[0134] Other useful nonionic surfactants include, but are not limitedto, the condensation products of C₈-C₂₂ alkyl alcohols with 2-50 molesof ethylene oxide per mole of alcohol. Examples of compounds of thistype include the condensation products of C₁₁-C₁₅ secondary alkylalcohols with 3-50 moles of ethylene oxide per mole of alcohol, whichare commercially-available as the Poly-Tergent SLF series from OlinChemicals or the TERGITOL® series from Union Carbide, i.e. TERGITOL®25-L-7, which is formed by condensing about 7 moles of ethylene oxidewith a C₁₂-C₁₅ alkanol.

[0135] Other nonionic surfactants, which may be employed in the wettingcomposition of the present invention, include the ethylene oxide estersof C₆-C₁₂ alkyl phenols such as (nonylphenoxy)polyoxyethylene ether.Particularly useful are the esters prepared by condensing about 8-12moles of ethylene oxide with nonylphenol, i.e. the IGEPAL® CO series(GAF Corp.).

[0136] Further non-ionic surface active agents include, but are notlimited to, alkyl polyglycosides (APG), derived as a condensationproduct of dextrose (D-glucose) and a straight or branched chainalcohol. The glycoside portion of the surfactant provides a hydrophilehaving high hydroxyl density, which enhances water solubility.Additionally, the inherent stability of the acetal linkage of theglycoside provides chemical stability in alkaline systems. Furthermore,unlike some non-ionic surface active agents, alkyl polyglycosides haveno cloud point, allowing one to formulate without a hydrotrope, andthese are very mild, as well as readily biodegradable non-ionicsurfactants. This class of surfactants is available from HorizonChemical under the trade names of APG-300, APG-350, APG-500, andAPG-500.

[0137] Silicones are another class of wetting agents available in pureform, or as microemulsions, macroemulsions, and the like. One exemplarynon-ionic surfactant group is the silicone-glycol copolymers. Thesesurfactants are prepared by adding poly(lower)alkylenoxy chains to thefree hydroxyl groups of dimethylpolysiloxanols and are available fromthe Dow Coming Corp as Dow Corning 190 and 193 surfactants (CTFA name:dimethicone copolyol). These surfactants function, with or without anyvolatile silicones used as solvents, to control foaming produced by theother surfactants, and also impart a shine to metallic, ceramic, andglass surfaces.

[0138] Anionic surfactants may also be used in the wetting compositionsof the present invention. Anionic surfactants are useful due to theirhigh detergency include anionic detergent salts having alkylsubstituents of 8 to 22 carbon atoms such as the water-soluble higherfatty acid alkali metal soaps, e.g., sodium myristate and sodiumpalmitate. A preferred class of anionic surfactants encompasses thewater-soluble sulfated and sulfonated anionic alkali metal and alkalineearth metal detergent salts containing a hydrophobic higher alkyl moiety(typically containing from about 8 to 22 carbon atoms) such as salts ofhigher alkyl mono or polynuclear aryl sulfonates having from about 1 to16 carbon atoms in the alkyl group, with examples available as theBio-Soft series, i.e. Bio-Soft D-40 (Stepan Chemical Co.).

[0139] Other useful classes of anionic surfactants include, but are notlimited to, the alkali metal salts of alkyl naphthalene sulfonic acids(methyl naphthalene sodium sulfonate, Petro AA, PetrochemicalCorporation); sulfated higher fatty acid monoglycerides such as thesodium salt of the sulfated monoglyceride of cocoa oil fatty acids andthe potassium salt of the sulfated monoglyceride of tallow fatty acids;alkali metal salts of sulfated fatty alcohols containing from about 10to 18 carbon atoms (e.g., sodium lauryl sulfate and sodium stearylsulfate); sodium C₁₄-C₁₆-alphaolefin sulfonates such as the Bio-Tergeseries (Stepan Chemical Co.); alkali metal salts of sulfated ethyleneoxyfatty alcohols (the sodium or ammonium sulfates of the condensationproducts of about 3 moles of ethylene oxide with a C₁₂-C₁₅ n-alkanol,i.e., the Neodol ethoxysulfates, Shell Chemical Co.); alkali metal saltsof higher fatty esters of low molecular weight alkylol sulfonic acids,e.g. fatty acid esters of the sodium salt of isothionic acid, the fattyethanolamide sulfates; the fatty acid amides of amino alkyl sulfonicacids, e.g. lauric acid amide of taurine; as well as numerous otheranionic organic surface active agents such as sodium xylene sulfonate,sodium naphthalene sulfonate, sodium toulene sulfonate and mixturesthereof.

[0140] A further useful class of anionic surfactants includes the8-(4-n-alkyl-2-cyclohexenyl)-octanoic acids, wherein the cyclohexenylring is substituted with an additional carboxylic acid group. Thesecompounds or their potassium salts, are commercially-available fromWestvaco Corporation as Diacid 1550 or H-240. In general, these anionicsurface active agents can be employed in the form of their alkali metalsalts, ammonium or alkaline earth metal salts.

[0141] Macroemulsions and Microemulsion of Silicone Particles

[0142] The wetting composition may further comprise an aqueousmicroemulsion of silicone particles. For example, U.S. Pat. No.6,037,407, “Process for the Preparation of Aqueous Emulsions of SiliconeOils and/or Gums and/or Resins” issued Mar. 14, 2000, disclosesorganopolysiloxanes in an aqueous microemulsion. Desirably, the wettingcomposition contains less than about 5 weight percent of a microemulsionof silicone particles based on the total weight of the wettingcomposition. More desirably, the wetting composition contains from about0.02 weight percent to about 3 weight percent of a microemulsion ofsilicone particles. Even more desirably, the wetting compositioncontains from about 0.02 weight percent to about 0.5 weight percent of amicroemulsion of silicone particles.

[0143] Silicone emulsions in general may be applied to the pre-moistenedwipe by any known coating method. For example, the pre-moistened wipemay be moistened with an aqueous composition comprising awater-dispersible or water-miscible, silicone-based component that iscompatible with the activating compound in the wetting composition.Further, the wipe can comprise a nonwoven web of fibers having awater-dispersible binder, wherein the web is moistened with a lotioncomprising a silicone-based sulfosuccinate. The silicone-basedsulfosuccinate provides gentle and effective cleansing without a highlevel of surfactant. Additionally, the silicone-based sulfosuccinateprovides a solubilization function, which prevents precipitation ofoil-soluble components, such as fragrance components, vitamin extracts,plant extracts, and essential oils.

[0144] In one embodiment of the present invention, the wettingcomposition comprises a silicone copolyol sulfosuccinate, such asdisodium dimethicone copolyol sulfosuccinate and diammonium dimethiconecopolyolsulfosuccinate. Desirably, the wetting composition comprisesless than about 2 percent by weight of the silicone-basedsulfosuccinate, and more desirably from about 0.05 percent to about 0.30percent by weight of the silicone-based sulfosuccinate.

[0145] In another example of a product comprising a silicone emulsions,Dow Coming 9506 powder may also be present in the wetting composition.Dow Coming 9506 powder is believed to comprise adimethicone/vinyldimethicone cross-polymer and is a spherical powder,which is said to be useful in controlling skin oils (see “New ChemicalPerspectives,” Soap and Cosmetics, Vol. 76, No. 3, March 2000, p. 12).Thus, a water-dispersible wipe, which delivers a powder effective incontrolling skin oil, is also within the scope of the present invention.Principles for preparing silicone emulsions are disclosed in WO97/10100, published Mar. 20, 1997.

[0146] Emollients

[0147] The wetting composition of the present invention may also containone or more emollients. Suitable emollients include, but are not limitedto, PEG 75 lanolin, methyl gluceth 20 benzoate, C₁₂-C₁₅ alkyl benzoate,ethoxylated cetyl stearyl alcohol, products marketed as Lambent waxWS-L, Lambent WD-F, Cetiol HE (Henkel Corp.), Glucam P20 (Amerchol),Polyox WSR N-10 (Union Carbide), Polyox WSR N-3000 (Union Carbide),Luviquat (BASF), Finsolv SLB 101 (Finetex Corp.), mink oil, allantoin,stearyl alcohol, Estol 1517 (Unichema), and Finsolv SLB 201 (FinetexCorp.).

[0148] An emollient can also be applied to a surface of the articleprior to or after wetting with the wetting composition. Such anemollient may be insoluble in the wetting composition and can beimmobile except when exposed to a force. For example, a petrolatum-basedemollient can be applied to one surface in a pattern, after which theother surface is wetted to saturate the wipe. Such a product couldprovide a cleaning surface and an opposing skin treatment surface.

[0149] The emollient composition in such products and other products ofthe present invention can comprise a plastic or fluid emollient such asone or more liquid hydrocarbons (e.g., petrolatum), mineral oil and thelike, vegetable and animal fats (e.g., lanolin, phospholipids and theirderivatives) and/or a silicone materials such as one or more alkylsubstituted polysiloxane polymers, including the polysiloxane emollientsdisclosed in U.S. Pat. No. 5,891,126, issued Apr. 6, 1999 to Osborn, IIIet al. Optionally, a hydrophilic surfactant may be combined with aplastic emollient to improve wettability of the coated surface. In someembodiments of the present invention, it is contemplated that liquidhydrocarbon emollients and/or alkyl substituted polysiloxane polymersmay be blended or combined with one or more fatty acid ester emollientsderived from fatty acids or fatty alcohols.

[0150] In an embodiment of the present invention, the emollient materialis in the form of an emollient blend. Desirably, the emollient blendcomprises a combination of one or more liquid hydrocarbons (e.g.,petrolatum), mineral oil and the like, vegetable and animal fats (e.g.,lanolin, phospholipids and their derivatives), with a silicone materialsuch as one or more alkyl substituted polysiloxane polymers. Moredesirably, the emollient blend comprises a combination of liquidhydrocarbons (e.g., petrolatum) with dimethicone or with dimethicone andother alkyl substituted polysiloxane polymers. In some embodiments ofthe present invention, it is contemplated that blends of liquidhydrocarbon emollients and/or alkyl substituted polysiloxane polymersmay be blended with one or more fatty acid ester emollients derived fromfatty acids or fatty alcohols. PEG-7 glyceryl cocoate, available asStandamul HE (Henkel Corp., Hoboken, N.J.), can also be considered.

[0151] Water-soluble, self-emulsifying emollient oils, which are usefulin the present wetting compositions, include the polyoxyalkoxylatedlanolins and the polyoxyalkoxylated fatty alcohols, as disclosed in U.S.Pat. No. 4,690,821, issued Sep. 1, 1987 to Smith et al. Thepolyoxyalkoxy chains desirably will comprise mixed propylenoxy andethyleneoxy units. The lanolin derivatives will typically comprise about20-70 such lower-alkoxy units while the C₁₂-C₂₀—fatty alcohols will bederivatized with about 8-15 lower-alkyl units. One such useful lanolinderivative is Lanexol AWS (PPG-12-PEG-50, Croda, Inc., New York, N.Y.).A useful poly(15-20)C₂-C₃-alkoxylate is PPG-5-Ceteth-20, known asProcetyl AWS (Croda, Inc.).

[0152] According to one embodiment of the present invention, theemollient material reduces undesirable tactile attributes, if any, ofthe wetting composition. For example, emollient materials, includingdimethicone, can reduce the level of tackiness that may be caused by theion-sensitive binder or other components in the wetting composition,thus serving as a detackifier.

[0153] Desirably, the wetting composition contains less than about 25weight percent of emollients based on the total weight of the wettingcomposition. More specifically, the wetting composition may compriseless than about 5 weight percent emollient, and most specifically lessthan about 2 weight percent emollient. More desirably, the wettingcomposition may contain from about 0.01 weight percent to about 8 weightpercent of emollients. Even more desirably, the wetting composition maycontain from about 0.2 weight percent to about 2 weight percent ofemollients.

[0154] In one embodiment, the wetting composition and/or pre-moistenedwipes of the present invention comprise an oil-in-water emulsioncomprising an oil phase containing at least one emollient oil and atleast one emollient wax stabilizer dispersed in an aqueous phasecomprising at least one polyhydric alcohol emollient and at least oneorganic water-soluble detergent, as disclosed in U.S. Pat. No.4,559,157, issued Dec. 17, 1985 to Smith et al., the entirety of whichis herein incorporated by reference.

[0155] Surface Feel Modifiers

[0156] Surface feel modifiers are used to improve the tactile sensation(e.g., lubricity) of the skin during use of the product. Suitablesurface feel modifiers include, but are not limited to, commercialdebonders; and softeners, such as the softeners used in the art oftissue making including quaternary ammonium compounds with fatty acidside groups, silicones, waxes, and the like. Exemplary quaternaryammonium compounds with utility as softeners are disclosed in U.S. Pat.No. 3,554,862, issued to Hervey et al. on Jan. 12, 1971; U.S. Pat. No.4,144,122, issued to Emanuelsson et al., Mar. 13, 1979, U.S. Pat. No.5,573,637, issued to Ampulski et al. Nov. 12, 1996; and U.S. Pat. No.4,476,323, issued to Hellsten et al., Oct. 9, 1984, the entirety of allof which is herein incorporated by reference. Desirably, the wettingcomposition contains less than about 2 weight percent of surface feelmodifiers based on the total weight of the wetting composition. Moredesirably, the wetting composition contains from about 0.01 weightpercent to about 1 weight percent of surface feel modifiers. Even moredesirably, the wetting composition contains from about 0.01 weightpercent to about 0.05 weight percent of surface feel modifiers.

[0157] Fragrances

[0158] A variety of fragrances may be used in the wetting composition ofthe present invention. Desirably, the wetting composition contains lessthan about 2 weight percent of fragrances based on the total weight ofthe wetting composition. More desirably, the wetting compositioncontains from about 0.01 weight percent to about 1 weight percent offragrances. Even more desirably, the wetting composition contains fromabout 0.01 weight percent to about 0.05 weight percent of fragrances.

[0159] Fragrance Solubilizers Further, a variety of fragrancesolubilizers may be used in the wetting composition of the presentinvention. Suitable fragrance solubilizers include, but are not limitedto, polysorbate 20, propylene glycol, ethanol, isopropanol, diethyleneglycol monoethyl ether, dipropylene glycol, diethyl phthalate, triethylcitrate, Ameroxol OE-2 (Amerchol Corp.), Brij 78 and Brij 98 (ICISurfactants), Arlasolve 200 (ICI Surfactants), Calfax 16L-35 (PilotChemical Co.), Capmul POE-S (Abitec Corp.), Finsolv SUBSTANTIAL(Finetex), and the like. Desirably, the wetting composition containsless than about 2 weight percent of fragrance solubilizers based on thetotal weight of the wetting composition. More desirably, the wettingcomposition contains from about 0.01 weight percent to about 1 weightpercent of fragrance solubilizers. Even more desirably, the wettingcomposition contains from about 0.01 weight percent to about 0.05 weightpercent of fragrance solubilizers.

[0160] Opacifiers

[0161] Suitable opacifiers include, but are not limited to, titaniumdioxide or other minerals or pigments, and synthetic opacifiers such asREACTOPAQUE® particles (available from Sequa Chemicals, Inc., Chester,S.C.). Desirably, the wetting composition contains less than about 2weight percent of opacifiers based on the total weight of the wettingcomposition. More desirably, the wetting composition contains from about0.01 weight percent to about 1 weight percent of opacifiers. Even moredesirably, the wetting composition contains from about 0.01 weightpercent to about 0.05 weight percent of opacifiers.

[0162] pH Control Agents

[0163] Suitable pH control agents for use in the wetting composition ofthe present invention include, but are not limited to, malic acid,citric acid, hydrochloric acid, acetic acid, sodium hydroxide, potassiumhydroxide, and the like. An appropriate pH range minimizes the amount ofskin irritation resulting from the wetting composition on the skin.Desirably, the pH range of the wetting composition is from about 3.5 toabout 6.5. More desirably, the pH range of the wetting composition isfrom about 4 to about 6. Desirably, the wetting composition containsless than about 2 weight percent of a pH adjuster based on the totalweight of the wetting composition. More desirably, the wettingcomposition contains from about 0.01 weight percent to about 1 weightpercent of a pH adjuster. Even more desirably, the wetting compositioncontains from about 0.01 weight percent to about 0.05 weight percent ofa pH adjuster.

[0164] Although a variety of wetting compositions, formed from one ormore of the above-described components, may be used with the wet wipesof the present invention, in one embodiment, the wetting compositioncontains the following components, given in weight percent of thewetting composition, as shown in Table 2 below: TABLE 2 WettingComposition Components Wetting Composition Component: Weight Percent:Deionized Water about 86 to about 98 Activating compound about 1 toabout 6 Preservative Up to about 2 Surfactant Up to about 2 SiliconeEmulsion Up to about 1 Emollient Up to about 1 Fragrance Up to about 0.3Fragrance solubilizer Up to about 0.5 pH adjuster Up to about 0.2

[0165] In another embodiment of the present invention, the wettingcomposition comprises the following components, given in weight percentof the wetting composition, as shown in Table 3 below: TABLE 3 WettingComposition Components Class of Wetting Specific Wetting CompositionComposition Component Weight Component: Component: Name: Percent:Vehicle Deionized Water about 86 to about 98 Activating Sodium Chlorideabout 1 to compound (Millport Ent., about 6 Milwaukee, WI) PreservativeGlycerin, IPBC and Mackstat H-66 Up to about 2 DMDM Hydantoin (McIntyreGroup, Chicago, IL) Surfactant Acyl Glutamate CS22 Up to about 2(Ajinomoto, Tokyo, Japan) Silicone Dimethiconol and DC1785 Up to about 1Emulsion TEA Dodecylbenezene (Dow Corning, (Detackifier/ SulfonateMidland, MI) Skin Feel agent) Emollient PEG-75 Lanolin Solulan L-575 Upto about 1 (Amerchol, Middlesex, NJ) Fragrance Fragrance Dragoco Up toabout 0.3 0/708768 (Dragoco, Roseville, MN) Fragrance Polysorbate 20Glennsurf L20 Up to about 0.5 solubilizer (Glenn Corp., St. Paul, MN) pHadjuster Malic Acid to pH 5 Up to about 0.2 (Haarman & Reimer, Tetrboro,NJ)

[0166] In another embodiment of the present invention, the wettingcomposition comprises the following components, given in weight percentof the wetting composition, as shown in Table 4 below: TABLE 4 AnExemplary Wetting Composition Class of Wetting Specific Wettingcomposition composition Component Weight Component: Component: Name:Percent: Vehicle Deionized Water about 93 Activating Sodium Chlorideabout 4 compound Preservative Glycerin, IPBC and Mackstat about 1 DMDMHydantoin H-66 Surfactant Acyl Glutamate CS22/ECS about 1 22P SiliconeDimethiconol and DC 1784/ about 0.5 Emulsion TEA DC 1785 DodecylbenzeneSulfonate Emollient PEG-75 Lanolin Solulan L-575 about 0.25 FragranceFragrance Dragoco about 0.05 Fragrance 0/708768 Fragrance Polysorbate 20Glennsurf L20 about 0.25 solubilizer pH adjuster Malic Acid to pH 5about 0.07

[0167] It should be noted that the above-described wetting compositionsof the present invention may be used with any one of the above-describedion-sensitive binder compositions of the present invention. Further, theabove-described wetting compositions of the present invention may beused with any other binder composition, including conventional bindercompositions, or with any known fibrous or absorbent substrate, whetherdispersible or not.

[0168] Strength Properties

[0169] Unless otherwise specified, tensile testing is performedaccording to the following protocol. Testing of dry product should beconducted under Tappi conditions (50% relative humidity, 73° F.) with aprocedure similar to ASTM-1117-80, section 7. Tensile tests areperformed with a constant crosshead speed tensile tester such as theThwing Albert 1256-100 tensile tester with an RSA-2 10-kg load cell.Specimens are cut to 3-inch widths and 6 inch lengths, and mountedbetween jaws with a 4-inch gauge length. The crosshead speed is 12inches per minute. Peak load (for tensile strength) and elongation atpeak load (for stretch) are measured. For cross direction (CD) tensiletests, the sample is cut in the cross direction. For machine direction(MD) tensile tests, the sample is cut in the machine direction.

[0170] Tensile tests in the dry state are reported for webs taken priorto application of the wetting composition. The machine direction drytensile strength is abbreviated as “MDDT,” and the cross direction drytensile strength as “CDDT.” The results can be reported as kg/3-in orconverted to units of g/in or g/2.54 cm.

[0171] Based on the dry weight of the specimen cut to the appropriatesize, an excess amount of wetting solution (4% saline solution with noother additives, unless otherwise specified) is applied to reach asolution add-on of 250-400%. The wetted specimens are then immediatelypassed through an Atlas Lab Wringer (Atlas Electric Devices Company,Chicago, Ill. No. 10404 LW-1, no load) to uniformly distribute thesolution in the sample and gently remove the excess solution to achievea final solution add-on of 200%. Several iterations or passes may beneeded to reach the add-on target depending on the sample. If an AtlasWringer is not available the wetted sample may be hand rolled using astainless steel cylinder to uniformly distribute the solution in thesample and gently remove the excess wetting solution. Alternatively, thewetting solution may be uniformly applied to the specimen by handspraying. In this case, the final solution add-on is again measuredgravimetrically only this time with the specimen placed on the balanceduring the application of the wetting solution. The completed,pre-moistened samples are then bagged in plastic to prevent dry-outbefore testing.

[0172] Cross direction wet tensile tests (CDWT) or machine direction wettensile strength (MDWT) are performed as described above using thepre-moistened sample as is, after the sample has equilibrated by sittingovernight in a sealed plastic bag. Alternatively, wet tensile resultscan be measured with an MTS Synergie 200 tensile tester using theTestworks™ 3.10 for Windows software. A 1-inch wide by 4-inch long stripcan be used for testing. The gauge length between the jaws of the testdevice may be 3 inches. Testing is operated at the specified cross headspeed of 12 in/min. The peak load for each of 10 samples was measuredand the average peak load in g/1″ reported in Table 29.

[0173] For tests related to strength loss in a premoistened weboccurring after exposure to a new solution, a container havingdimensions of 200 mm by 120 mm and deep enough to hold 1000 ml is filledwith 700 ml of the selected soak solution. No more than 108 squareinches of sample are soaked in the 700 ml of soaking solution, dependingon specimen size. The premoistened specimens, that have equilibratedovernight, are immersed in the soak solution and then allowed to soakundisturbed for a specified time period (typically 1 hour). At thecompletion of the soak period, samples are carefully retrieved from thesoak solution, allowed to drain, and then tested immediately asdescribed above (i.e., the sample is immediately mounted in the tensiletester and tested, without being passed through the wringer). In caseswith highly dispersible materials, the samples often cannot be retrievedfrom the soaking solution without falling apart. The soaked tensilevalues for such samples are recorded as zero for the correspondingsolution. The average of all tests conducted, both zero and non-zero,are reported.

[0174] For the deionized soaked cross-direction wet tensile test,S-CDWT, the sample is immersed in deionized water for 1 hour and thentested. For the hard-water soaked cross-direction wet tensile test,S-CDWT-M (M indicating divalent metal ions), the sample is immersed inwater containing 200 ppm of Ca⁺⁺/Mg⁺⁺ in a 2:1 ratio (133 ppm Ca++/67ppm Mg++) prepared from calcium chloride and magnesium chloride, soakedfor one hour and then tested. For the medium hard water soakedcross-direction wet tensile test, MS-CDWT-M, the sample is immersed inwater containing 50 ppm of Ca⁺⁺/Mg⁺⁺ in a 2:1 ratio, soaked for one hourand then tested. Testing done with other time increments or soakingsolutions should be so indicated to prevent confusion with the S-CDWT orS-CDWT-M tests.

[0175] In one embodiment of the present invention, wet wipes areproduced using the above-described wetting composition in Table 3 and anair-laid fibrous material comprising about 80 weight percent of bleachedkraft fibers and 20 weight percent of any one of the above-describedion-sensitive binder compositions of the present invention, wherein theweight percentages are based on the total weight of the dry nonwovenfabric. In a further embodiment of the present invention, wet wipes areproduced using the above-described wetting composition in Table 3 and anair-laid fibrous material comprising 90 weight percent of softwoodfibers and 10 weight percent of an ion-sensitive binder compositionscomprising acrylic acid terpolymers or a copolymer substantially free ofacrylic acid monomers, wherein the weight percentages are based on thetotal weight of the dry nonwoven fabric. The amount of wettingcomposition added to the nonwoven fabric, relative to the weight of thedry nonwoven fabric in these embodiments, is desirably about 180 percentto about 240 weight percent.

[0176] Desirably, in one embodiment, the wet wipes of the presentinvention possess an in-use wet tensile strength (CDWT) of at least 100g/in, and a tensile strength of less than about 30 g/in after beingsoaked in water having a concentration of Ca²⁺ and/or Mg²⁺ ions of about50 ppm for about one hour (MS-CDWT-M). More desirably, the wet wipespossess an in-use wet tensile strength of at least 300 g/in (CDWT), anda tensile strength of less than about 30 g/in after being soaked inwater having a concentration of Ca²⁺ and/or Mg²⁺ ions of about 50 ppmfor about one hour (MS-CDWT-M). In a further embodiment, the wet wipesdesirably possess an in-use wet tensile strength of at least 200 g/in(CDWT), and a tensile strength of less than about 20 g/in after beingsoaked in water having a concentration of Ca²⁺ and/or Mg²⁺ ions of about200 ppm for about one hour (S-CDWT-M). Even more desirably, the wetwipes possess an in-use wet tensile strength of at least 300 g/in, and atensile strength of less than about 20 g/in after being soaked in waterhaving a concentration of Ca²⁺ and/or Mg²⁺ ions of about 200 ppm forabout one hour (S-CDWT-M).

[0177] Desirably, in another embodiment, the wet wipes of the presentinvention possess an in-use wet tensile strength (CDWT) of at least 100g/in, and a tensile strength of less than about 70 g/in after beingsoaked in water having a concentration of Ca²⁺ and/or Mg²⁺ ions of about10 ppm for about one hour (MS-CDWT-M). Additionally, these wet wipeshave a tensile strength of less than about 60% of the original CDWTafter being soaked in water having a concentration of Ca²⁺ and/or Mg²⁺ions of about 200 ppm for about one hour. More desirably, the wet wipespossess an in-use wet tensile strength (CDWT) of at least 200 g/in, anda tensile strength of less than about 50 g/in after being soaked inwater having a concentration of Ca²⁺ and/or Mg²⁺ ions of about 10 ppmfor about one hour (MS-CDWT-M). Additionally, these wet wipes have atensile strength of less than about 40% of the original CDWT after beingsoaked in water having a concentration of Ca²⁺ and/or Mg²⁺ ions of about200 ppm for about one hour. Even more desirably, the wet wipes possessan in-use wet tensile strength (CDWT) of at least 300 g/in, and atensile strength of less than about 30 g/in after being soaked in waterhaving a concentration of Ca²⁺ and/or Mg²⁺ ions of about 10 ppm forabout one hour (MS-CDWT-M). Additionally, these wet wipes have a tensilestrength of less than about 20% of the original CDWT after being soakedin water having a concentration of Ca²⁺ and/or Mg²⁺ ions of about 200ppm for about one hour.

[0178] Desirably, the wet wipes treated with the binder material of thepresent invention including the acrylic acid terpolymer possess anin-use wet tensile strength of at least 100 g/in for a 1 inch widthsample in the cross machine direction when soaked with 10% to 400% byweight wet wipes solution containing more than 0.3% by weight monovalention (NaCl) concentration and a tensile strength of less than about 30g/in after being soaked in deionized water for about one hour. Moredesirably, the wet wipes treated with the binder material of the presentinvention including the acrylic acid terpolymer possess an in-usetensile strength of at least 200 g/in for a 1 inch width sample in thecross machine direction when soaked with 10% to 400% by weight wet wipessolution containing more than 0.3% by weight monovalent ion (NaCl)concentration and a tensile strength of less than about 30 g/in afterbeing soaked in deionized water for about one hour.

[0179] In a further embodiment, the wet wipes treated with the bindermaterial of the present invention including the sulfonate anion modifiedacrylic acid terpolymer desirably possess an in-use tensile strength ofat least 200 g/in for a 1 inch width sample in the cross machinedirection when soaked with 10% to 400% by weight wet wipes solutioncontaining more than 1% by weight monovalent ion (NaCl) concentrationand a tensile strength of less than about 30 g/in after being soaked inwater having a concentration of Ca²+and/or Mg²⁺ ions of about 50 ppm forabout one hour. Even more desirably, the wet wipes treated with thebinder material of the present invention including the sulfonate anionmodified acrylic acid terpolymer possess an in-use tensile strength ofat least 200 g/in for a 1 inch width sample in the cross machinedirection when soaked with 10% to 400% by weight wet wipes solutioncontaining more than 1% by weight monovalent ion (NaCl) concentrationand a tensile strength of less than about 30 g/in after being soaked inwater having a concentration of Ca²⁺ and/or Mg²⁺ ions of about 200 ppmfor about one hour.

[0180] Products with high basis weights or wet strengths than flushablewet wipes may have relatively higher wet tensile strength. For example,products such as pre-moistened towels or hard-surface cleaning wipes mayhave basis weights above 70 gsm, such as from 80 gsm to 150 gsm. Suchproducts can have CDWT values of 500 g/in or greater, with S-CDWT valuesof about 150 g/in or less, more specifically about 100 g/in or less, andmost specifically about 50 g/in or less, with similar ranges possiblefor S-CDWT-M.

[0181] Dispersibility

[0182] Prior efforts to measure dispersibility of webs, whether dry orpremoistened, have commonly relied on systems in which the web wasexposed to shear while in water, such as measuring the time for a web tobreak up while being agitated by a mechanical mixer. The constantexposure to shear offers an unrealistic and overly optimistic test forproducts designed to be flushed in a toilet, where the level of shear isweak and extremely brief. Once the product has passed through the neckof the toilet and entered a septic tank, shear rates may be negligible.Further, the product may not be fully wetted with water from the toiletbowl when it is flushed, or rather, there may not have been adequatetime for the wetting composition of the product to have been replacedwith the water of the toilet bowl when the momentary shear of flushingis applied. Thus, previous measurements of dispersibility could suggestthat a product is dispersible when, in fact, it may be poorly suited forseptic system.

[0183] For a realistic appraisal of dispersibility, it is believed thata relatively static measure is needed to better simulate the low shearthat real products will experience once they have become fully wettedwith water from the toilet. Thus, a test method for dispersibility hasbeen developed which does not rely on shear and which provides animproved means of assessing suitability of a product for a septicsystem. In this method, the tensile strength of a product is measured inits original, wetted form (the CDWT measurement described above) andafter the product has been soaked in a second solution for one hour(either the S-CDWT or S-CDWT-M test). The second solution can be eitherdeionized water for determination of the “Deionized Dispersibility”value or hard water (according to the S-CDWT-M test) for determinationof the “Hard Water Dispersibility” value. In either case, theDispersibility is defined as (1 minus the ratio of the cross-directionwet tensile strength in the second solution divided by the originalcross-direction wet tensile strength)*100%. Thus, if a pre-moistenedwipe loses 75% of its CD wet tensile strength after soaking in hardwater for one hour, the Hard Water Dispersibility is (1−0.25)*100% =75%.The articles of the present invention can have a DeionizedDispersibility of 80% or greater, more specifically 90% or greater,specifically still 95% or greater, and can have a DeionizedDispersibility of about 100%. The articles of the present invention canhave a Hard Water Dispersibility of 70% or greater, more specifically80% or greater, specifically still about 90% or greater, and can have aDeionized Dispersibility of about 100%.

[0184] Or, as set forth previously, the articles of the presentinvention would desirably have a soaked CDWT (S-CDWT) in hard water (200ppm of multivalent ions) after 1 hour of less than about 60% of theoriginal in-use CDWT for the article. More desirably, the articles ofthe present invention have a S-CDWT in hard water after 1 hour of lessthan about 50% of the original in-use CDWT for the article and moredesirably less than about 40%. Even more desirably, the articles of thepresent invention have a S-CDWT in hard water after 1 hour of less thanabout 30% of the original in-use CDWT for the article and more desirablyless than about 20%. Most desirably, the articles of the presentinvention have a S-CDWT in hard water after 1 hour of less than about10% of the original in-use CDWT for the article.

[0185] Method of Making Wet Wipes

[0186] The pre-moistened wipes of the present invention can be made inseveral ways. In one embodiment, the ion-sensitive polymer compositionis applied to a fibrous substrate as part of an aqueous solution orsuspension, wherein subsequent drying is needed to remove the water andpromote binding of the fibers. In particular, during drying, the bindermigrates to the crossover points of the fibers and becomes activated asa binder in those regions, thus providing acceptable strength to thesubstrate. For example, the following steps can be applied:

[0187] 1. Providing an absorbent substrate that is not highly bonded(e.g., an unbonded airlaid, a tissue web, a carded web, fluff pulp,etc.).

[0188] 2. Applying an ion-sensitive polymer composition to thesubstrate, typically in the form of a liquid, suspension, or foam.

[0189] 3. Applying a co-binder polymer to the substrate.

[0190] 4. Drying the substrate to promote bonding of the substrate. Thesubstrate may be dried such that the peak substrate temperature does notexceed 160° C., or 140° C., or 120° C., 110° C., or 100° C. In oneembodiment, the substrate temperature does not exceed 80° C. or 60° C.

[0191] 5. Applying a wetting composition to the substrate.

[0192] 6. Placing the wetted substrate in roll form or in a stack andpackaging the product.

[0193] Application of the co-binder polymer can be done simultaneouslywith application of the binder composition by previously mixing the two,or the co-binder polymer can be added before or after the binder isapplied. The other steps are desirably conducted in the order shownabove.

[0194] Application of the ion-sensitive polymer composition to thesubstrate can be by means of spray; by foam application; by immersion ina bath; by curtain coating; by coating and metering with a wire-woundrod; by passage of the substrate through a flooded nip; by contact witha pre-metered wetted roll coated with the binder solution; by pressingthe substrate against a deformable carrier containing the ion-sensitivepolymer composition such as a sponge or felt to effect transfer into thesubstrate; by printing such as gravure, inkjet, or flexographicprinting; and any other means known in the art.

[0195] In the use of foams to apply a binder or co-binder polymer, themixture is frothed, typically with a foaming agent, and spread uniformlyon the substrate, after which vacuum is applied to pull the froththrough the substrate. Any known foam application method can be used,including that of U.S. Pat. No. 4,018,647, “Process for the Impregnationof a Wet Fiber Web with a Heat Sensitized Foamed Latex Binder,” issuedApr. 19, 1977 to Wietsma, the entirety of which is herein incorporatedby reference. Wietsma discloses a method wherein a foamed latex isheat-sensitized by the addition of a heat-sensitizer such as functionalsiloxane compounds including siloxane oxyalkylene block copolymers andorganopolysiloxanes. Specific examples of applicable heat-sensitizersand their use thereof for the heat sensitization of latices aredescribed in the U.S. Pat. Nos. 3,255,140; 3,255,141; 3,483,240 and3,484,394, all of which are incorporated herein by reference. The use ofa heat-sensitizer is said to result in a product having a very soft andtextile-like hand compared to prior methods of applying foamed latexbinders.

[0196] The amount of heat-sensitizer to be added is dependent on, interalia, the type of latex used, the desired coagulation temperature, themachine speed and the temperatures in the drying section of the machine,and will generally be in the range of about 0.05 to about 3% by weight,calculated as dry matter on the dry weight of the latex; but also largeror smaller amounts may be used. The heat sensitizer can be added in suchan amount that the latex will coagulate far below the boiling point ofwater, for instance at a temperature in the range of 35° C. to 95° C.,or from about 35° C. to 65° C.

[0197] Without wishing to be bound by theory, it is believed that adrying step after application of the binder solution and beforeapplication of the wetting composition enhances bonding of a fibroussubstrate by driving the binder to fiber crossover points as moisture isdriven off, thus promoting efficient use of the binder. However, in analternative method, the drying step listed above is skipped, and theion-sensitive polymer composition is applied to the substrate followedby application of the wetting composition without significantintermediate drying. In one version of this method, the ion-sensitivepolymer composition selectively adheres to the fibers, permitting excesswater to be removed in an optional pressing step without a significantloss of the binder from the substrate. In another version, nosignificant water removal occurs prior to application of the wettingcomposition. In yet another alternative method, the ion-sensitivepolymer composition and the wetting composition are appliedsimultaneously, optionally with subsequent addition of salt or otheractivating compounds to activate or further activate the binder.

[0198] As used herein, the “thickness” of a web is measured with a 3-inacrylic plastic disk connected to the spindle of a Mitutoyo DigimaticIndicator (Mitutoyo Corporation, 31-19, Shiba 5-chome, Minato-ku, Tokyo108, Japan) and which delivers a net load of 0.05 psi to the samplebeing measured. The Mitutoyo Digimatic Indicator is zeroed when the diskrests on a flat surface. When a sample having a size at least as greatas the acrylic disk is placed under the disk, a thickness reading can beobtained from the digital readout of the indicator. Place and center thespecimen under the acrylic disk being careful to avoid any creases orwrinkles. Gently lower the platen, wait 3 seconds, then record thethickness to the nearest 0.1 mm. Re-zero the indicator after eachreading. The average of 10 measurements is reported. Water-dispersiblesubstrates of the present invention can have any suitable thickness,such as from about 0.1 mm to about 5 mm. For wet wipes, thicknesses canbe in the range of about 0.2 mm to about 1 mm, more specifically fromabout 0.3 mm to about 0.8 mm. Thickness can be controlled, for example,by the application of compaction rolls during or after web formation, bypressing after binder or wetting composition has been applied, or bycontrolling the tension of winding when forming a roll good.

[0199] The use of the platen method to measure thickness gives anaverage thickness at the macroscopic level. Local thickness may vary,especially if the product has been embossed or has otherwise been givena three-dimensional texture.

[0200] The thicker the wet wipe the better as a sheet that is too thinmay not provide an effective barrier between the user of the product andthe surface being cleaned. At sheet thicknesses less than about 0.25 mm,the sheet would be considered too thin or flimsy. Accordingly, the wetwipe sheets of the present invention desirably have a thickness greaterthan about 0.25 mm. More desirably, the wet wipe sheets of the presentinvention have a thickness greater than about 0.3 mm. Most desirably,the wet wipe sheets of the present invention have a thickness greaterthan about 0.4 mm.

[0201] Wet Tensile Strength

[0202] Wet wipes made according to the present invention desirably havea wet tensile strength sufficient such that the wipes may be usedwithout breaking or tearing. Accordingly, the wipes of the presentinvention desirably have a wet tensile strength of greater than about100 g/in². More desirably, the wet wipes have a wet tensile strength ofgreater than about 200 g/in². Most desirably, the wet wipes have a wettensile strength of greater than about 300 g/in².

[0203] Wet tensile results were obtained with an MTS Synergie 200tensile tester using the TestworksTM 3.10 for Windows software. A 1-inchwide by 4-inch long strip was used for testing. The gauge length betweenthe jaws of the test device was 3 inches. Testing was operated at thespecified cross head speed of 12 in/min. The peak load for each of 10samples was measured and the average peak load in g/1″ reported in Table29.

[0204] Cup Crush

[0205] The laboratory conditions under which testing was performedgenerally adhere to ASTM E 171, “Standard Atmospheres for Conditioningand Testing Materials”, as well as 21 CFR 58.61-63, “Good laboratorypractices for nonclinical laboratory studies” and CFR 211.160(b)(4),“Current Good Manufacturing Practices for Finished Pharmaceuticals”.

[0206]FIGS. 4 and 5 show a cup-crush testing system 1100 which includesa cup forming assembly 1102 and force testing unit 1103. The forcetesting unit 1103 includes a force sensor 1104 to which is cantilevereda rigid rod 1105. A hemispherical foot 1108 is positioned at the freeend of rod 1105 (The foot actual looks more like a rounded off rod orfinger rather than the inverted mushroom depicted in the figure) Forcesensor 1104 includes electronics and mechanics for measuring the forceexperienced at foot 1108 and transferred through rigid rod 1105. Theassembly 1102 includes mating, top-hat shaped former cups 1110 and 1112,which grip a sheet 1202 (such as wet-wipe 1000), at least four points.The four corners 1106 of sheet 1202 extend outside of the assembly 1102.The cup 1112 is removed after forming sheet 1202 into a cup. A grippingring 1114 holds the formed sheet 1202 in cup 1110 during testing.

[0207] One measure of the softness of a non-woven fabric sheet 1202 isdetermined according to the “cup crush” test by system 1100. The cupcrush test evaluates fabric stiffness by measuring the peak load (alsocalled the “cup crush load” or just “cup crush”) required for a 1.6 cmdiameter hemispherically shaped foot 1108 to crush the wipe 1202 shapedinto an approximately 3.2 cm diameter by 3.2 cm tall cup shape, whilethe now cup shaped fabric is surrounded by an approximately 3.2 cmdiameter cylinder cup 1110 to maintain a uniform deformation of the cupshaped fabric 1102. There can be gaps between the ring 1114 and formingcup 1110, but at least four corners 1106 must be fixedly pinched therebetween. The foot 1108 and cylinder cup 1110 are aligned to avoidcontract between the cup walls and the foot that could affect thereadings. The load is measured in grams, and recorded a minimum oftwenty times per second while the foot is descending at a rate of about406 mm per minute. The cup crush test provides a value for the totalenergy required to crush a sample (the “cup crush energy”) which is theenergy over a 2.0 cm range beginning 0.5 cm below the top of the fabriccup, i.e., the area under the curve formed by the load in grams on oneaxis and the distance the foot travels in millimeters on the other. Cupcrush energy is reported in gm-mm (or inch-pounds). A lower cup crushvalue indicates a softer material. A suitable device for measuring cupcrush is a model 2700096 load cell (10N) available from the MTS SystemsCorporation of Minneapolis, Minn. The cup crush (cup crush load) valuesreported in the Examples are the average of 15 tests, each conducted ona previously untested sample.

[0208] Since cup crush is a measure of the softness and flexibility ofthe product, the lower the value, the softer and more flexible the wetwipe will be, and therefore the more desirable the product. As such, thewet wipes of the present invention desirably have a cup crush of lessthan about 40 g. More desirably, the wet wipes have a cup crush of lessthan about 35 g and even more desirably less than about 30 g. Even moredesirably, the wet wipes have a cup crush of less than about 25 g andmore desirably less than about 20 g. More desirably, the wet wipes havea cup crush of less than about 15 g and more desirably less than about10 g.

[0209] Opacity Measurement

[0210] Opacity is a measure of the tendency of a material to prevent thetransmission of light. A wipe with a low opacity allows more light topass through it, and therefore appears more transparent than a wipe of ahigher opacity. The opacity of a pre-moistened wipe can be measuredusing a BYK-Gardner Color-Guide Sphere Spin Spectrophotometer. Thecalibrated spectrophotometer is configured with a CIE standardilluminate A and 2° observer. The instrument uses a d/8° and 45/0geometry (diffuse illumination at 8° and 45° angles). The opacity ofpre-moistened wipes are measured “as is”. The wipes are testedindividually; first measuring against a 100 mm×100 mm black glassstandard and then against a 90 mm×90 mm Russian Opel MC-20 whitestandard. A Black Derlin holder is used for total hemisphericalreflectance of 380-760 nm at 10 nm intervals. The opacity is calculatedand recorded from the digital readout on the spectrophotometer. A totalof 10 wipes are tested individually in an identical manner and theresults averaged.

[0211] The products wet opacity is desirably higher as the wet opacityprovides an indication that the wet wipe will be able to perform itsdesired function without breaking or otherwise tearing. And wet opacityis generally lower than dry opacity as the addition of the reduces theamount of light scattering in the product resulting in lower wetopacities than a corresponding dry opacity for the same product.Accordingly, the wet wipes of the present invention desirably have a wetopacity of greater than about 20%. More desirably, the wet wipes of thepresent invention desirably have a wet opacity of greater than about35%.

[0212] The present invention is further illustrated by the followingexamples, which are not to be construed in any way as imposinglimitations upon the scope thereof. On the contrary, it is to be clearlyunderstood that resort may be had to various other embodiments,modifications, and equivalents thereof which, after reading thedescription herein, may suggest themselves to those skilled in the artwithout departing from the spirit of the present invention and/or thescope of the appended claims.

EXAMPLE 1 Preparation of Sulfonate Anion Modified Acrylic AcidTerpolymer

[0213] Acrylic acid (43.3 g, 0.60 mol), AMPS (10.7 g, 0.052 mol), butylacrylate (35.2 g, 0.27 mol), and 2-ethylhexyl acrylate (20 g, 0.11 mol)were dissolved in 55 g of acetone/water (70/30) mixture. An initiator,2,2-azobisisobutyronitrile (AIBN) (0.51 g, 3.1×10⁻³ mol), was dissolvedin 20 ml of acetone. The monomer solution was deoxygenated by bubblingN₂ through the solution for 20 minutes. To a 1000 ml three-neck roundbottom flask, equipped with a condenser, two addition funnels and amagnetic stirrer, was added 120 g of an acetone/water (70/30) mixture.The solvent was heated to gentle reflux under nitrogen. Monomers andinitiator were added simultaneously from the addition funnels over aperiod of two hours. Polymerization was allowed to proceed for anadditional two hours, at the end of which, the addition funnels andcondenser were replaced with a distillation head and a mechanical stirrod to remove acetone. A steady stream of N₂ was kept duringdistillation while the temperature was increased gradually from about65° C. to about 90° C. When the distillation was completed, 400 g ofdeionized water was added to reduce the viscosity of the polymersolution. A hazy, but uniform solution was obtained.

[0214] A total of nine polymers (Samples 1-9) were synthesized using theabove-described procedure. NaOH (2.1 g, 0.052 mol) in 20 ml of water wasadded at room temperature to neutralize the AMPS component in thesamples. The compositions of Samples 1-9 are summarized in Table 5below. All percentages are given in mole percent. TABLE 5 SulfonateAnion Modified Acrylic Acid Terpolymers Sample % AMPS % NaAMPS % AA % BA% EHA 1 0.0 3.0 64.0 22.5 10.5 2 0.0 3.5 63.5 22.5 10.5 3 0.0 3.9 62.124.6 9.4 4 0.0 4.0 57.0 26.5 12.5 5 0.0 4.2 64.7 19.7 11.4 6 0.0 5.058.0 26.5 10.5 7 0.0 4.0 63.0 21.5 11.5 8 0.0 5.0 59.0 25.5 10.5 9 0.05.0 60.0 24.5 10.5

EXAMPLE 2 Preparation of an Acrylic Acid Terpolymer

[0215] An acrylic acid terpolymer was produced using the polymerizationprocedure outlined in Example 2 of U.S. Pat. No. 5,312,883. Thefollowing monomers were used: acrylic acid (50 g, 0.69 mol), butylacrylate (25 g, 0.20 mol), and 2-ethylhexyl acrylate (25 g, 0.14 mol).The polymer was neutralized with 0.1 mole sodium hydroxide.

EXAMPLE 3 Preparation of Ion-Sensitive Polymer Formulation

[0216] The polymers prepared in Table 5, Sample 9 and Example 2 abovewere combined with Dur-O-Set RB to form the ion-sensitive polymerformulations of the present invention. The polymer formulations wereprepared as shown in Table 6 below. TABLE 6 Ion-Sensitive PolymerFormulations % Terpolymer % Modified Terpolymer Sample (Example 2)(Table 5, Sample 9) % EVA 1 85.0 0.0 15.0 2 0.0 85.0 15.0 3 65.0 0.035.0 4 0.0 65.0 35.0 5 95.0 0.0 5.0 6 0.0 95.0 5.0 7 55.0 0.0 45.0 8 0.055.0 45.0 9 75.0 0.0 25.0 10 0.0 75.0 25.0

EXAMPLE 4 Solubility of Ion-Sensitive Polymer Formulation

[0217] The sensitivity of the polymer formulations of Example 3 todivalent cations present in hard water were measured. Samples 1-10 ofExample 3 are placed in a number of CaCl₂ solutions with a Ca²⁺concentration varying from <10 to 200 ppm. Following soaking for anhour, the solubility of each polymer is noted. The solubility resultsare given below in Table 7. TABLE 7 Solubility Results Solubility inCa²⁺ Sample <10 ppm 50 ppm 100 ppm 200 ppm Sample 1 100 94 78 12 Sample2 100 100 98 91 Sample 3 100 60 36 2 Sample 4 99 100 97 90 Sample 5 10097 88 19 Sample 6 100 100 99 90 Sample 7 89 42 31 0 Sample 8 100 96 9690 Sample 9 100 73 78 7 Sample 10 100 100 100 90

[0218] In every case the film cast from the blend containing NaAMPS ismore soluble than the film containing the acrylic acid terpolymer,especially as the calcium ion concentration increases.

EXAMPLE 5 Testing the Binding Strength of Polymer Formulations with andWithout Crosslinking

[0219] For the pilot scale trials we used pulp based (CF 405 or NB 416pulp form Weyerhaeuser) airlaid base-sheets bound together with 2-5%bico fibers. The bico fibers were either Type-255 (from KoSa Fibers ofSalisbury, N.C.) with an activated polyethylene sheath and a polyestercore or Danaklon fibers (from FiberVisions of Varde, Denmark) with apolyethylene sheath and a polypropylene core. Both kinds of bico fiberswere 2-3 denier and cut to 6 mm length. The binder formulations wereapplied by spraying 12-15 weight percent solutions on to both sides ofthe above base-sheet. The strengths of the base-sheets under variousconditions are reported after subtracting the base strength of the webdue to the bico fibers. Table 8 reports the strengths of the base-sheetswith different formulations in 0.4 weight percent NaCl (CDWT) as well asafter a one hour soak in deionized water (S-CDWT): TABLE 8 TensileStrength EVA Binder Oven % Cross- BW Add-On Temp CDWT S-CDWT SampleTerpolymer % EVA linkable? (gsm) (%) (° C.) (g/in) (g/in) 1 85 15 Yes 7022 400 413 112 2 65 35 Yes 70 22 400 467 375 3 85 15 Yes 71 23 400 444116 4 85 15 Yes 76 28 400 518 143 5 85 15 No 70 22 400 430 21 6 85 15Yes 73 25 350 336 60 7 65 35 Yes 67 18 350 332 237 8 65 35 Yes 69 21 350268 165 9 85 15 Yes 68 20 350 219 35 10 65 35 Yes 67 19 350 199 74 11 8515 No 69 21 350 226 20 12 65 35 No 67 19 350 196 29

[0220] All the above codes would wet out better on first insult relativeto a binder formulation containing 100% acrylic acid terpolymer. Also,the binder formulations which contain the EVA, spray much better than100% acrylic acid terpolymer, leading to much improved binderdistribution and penetration on the substrate. Significantly, thoseformulations that were not crosslinkable; i.e., Samples 5, 11 and 12,had S-CDWTs of less than 30 g/in.

EXAMPLE 6

[0221] Binder formulations are prepared having the compositions shown inTable 9 below. The binder formulations at 12 weight percent solids aresprayed on both sides of an airlaid web. The airlaid web is based onpulp (CF 405 from Weyerhaeuser). Table 9 shows the strength of thebase-sheet in 0.9% NaCl solution (CDWT) and after a one hour soak indeionized water (S-CDWT). The effect on strength after aging the samplesin salt solution over a period of up to 16 weeks is also shown. Apreservative, such as Mackstat H66, is added to the samples to preventmold growth on the basesheets as they age in the salt solution. TABLE 9Tensile Strength of Base-Sheet % % BW Binder Add- Oven Temp Aging TimeCDWT S-CDWT Sample Terpolymer EVA (gsm) On (%) (° C.) (Weeks) (g/in)(g/in) 1 85 15 73 25 440 0 488 14 2 85 15 73 25 440 16 393 11 3 65 35 6425 440 0 358 16 4 65 35 64 25 440 12 369 21 5 55 45 64 25 440 0 364 28 655 45 64 25 440 12 354 32

[0222] The results in Table 9 indicate that the web does not loseinitial properties even after extensive aging in the in-use saltsolution when Dur-O-Set RB is used as the EVA. If a crosslinkable agentis present in the EVA, lower dispersibility results after aging thesamples for a few weeks.

EXAMPLE 7

[0223] In FIG. 1 is shown the strength properties of the NaAMPS modifiedterpolymer, which is also dispersible in hard water (up to 200 ppmCa⁺⁺/Mg⁺⁺ solution). A base-sheet based on 75 weight percent NaAMPSmodified acrylic acid terpolymer (SSB) and 25 weight percent EVA(Dur-O-Set® RB) exhibits very good strength during use (in 1.5% or 4.0%NaCl solution) and disperses in very hard water. SSB-4 dispersed in hardwater in 10 minutes. SSB-5 dispersed in hard water in 3 hours.NaAMPS-SSB is more viscous relative to Lion-SSB.

[0224] Tensile results for Examples 5 through 7 were obtained with anMTS tensile test device, the MTS 500/S unit (MTS Systems, Research Park,N.C.) using the Testworks™ 3.10 for Windows software. Instead of thenormal 3-inch strip for testing, a 1-inch wide strip was used, cut to 6inches in length. The gauge length between the rubber-coated jaws of thetest device was 3 inches. Testing was operated at the specifiedcrosshead speed of 12 in/min. The MTS device with the modified testprocedure generally gives comparable results to the tensile testprotocol previously described using 3-inch wide samples and theThwing-Albert tester.

EXAMPLE 8

[0225] The addition of the co-binder polymer to the ion-sensitivepolymer reduces the shear viscosity of the polymer blend compared to theshear viscosity of the ion-sensitive polymer alone. Table 10 illustratesthe effect of the addition of various co-binder polymers to an acrylicacid terpolymer (SSB-2) in accordance with the present invention. TABLE10 Effect of the Addition of Various Co-Binder Polymers to SSB-2 PolymerBlend Viscosity @ 100 sec⁻¹ 18 weight percent SSB-2 solids Too high tomeasure: >100,000 cps      15 weight percent sodium polyacrylate solids10,000 cps    (MW = 250,000, 50% neutralization) 12 weight percent neatSSB-2 80 cps 12 weight percent blend of 80 parts by wt. 25 cps SSB-2 and20 parts by wt. Rhoplex NW 1715K 12 weight percent blend of 80 parts bywt. 28 cps SSB-2 and 20 parts by wt. Rovene 12 weight percent blend of80 parts by wt. 20 cps SSB-2 and 20 parts by wt. Dur-O-Set RB

[0226] Table 10 shows that the addition of Rhoplex® NW 1715K, Rovene®4817 and Dur-O-Set® RB significantly reduce the shear viscosity of theSSB-2 acrylic acid terpolymer alone. The reduction in viscosity is notdue to a mere dilution of the SSB-2, because the addition of sodiumpolyacrylate resulted in a significant increase in the shear viscosityof the SSB-2.

EXAMPLE 9

[0227] Dried solid bars were prepared from Rhoplex® NW 1715K, Rovene®4817 and Dur-O-Set® RB. The bars were prepared by pouring a quantity ofthe polymer into a rectangular silicone mold an open rectangularsilicone mold 1 cm wide, 4 cm long, and 3 mm deep. The polymer in themold was then heated at 60° C. overnight. The dried polymer in the moldwas then placed in a container with 30 ml of deionized water at about23° C. and allowed to sit for one hour. None of the bars were dispersedin the deionized water.

[0228] Bar samples were then prepared from the sulfonate anion modifiedacrylic acid terpolymer (NaAMPS+SSB) blended separately with Rhoplex® NW1715K, Rovene® 4817 and Dur-O-Set® RB. The polymer blends were made from75% by weight sulfonate anion modified acrylic acid terpolymer and 25%by weight of the co-binder polymers. The bar samples were prepared inthe same manner as described above. The bar samples were then added todeionized water. Each of the bar samples made from the following polymerblends; i.e., NaAMPS+SSB/Rhoplex NW 1715K, NaAMPS+SSB/Rovene 4817 andNaAMPS+SSB/Dur-O-Set RB, dispersed in the deionized water within onehour.

EXAMPLE 10

[0229] A substrate in the form of an airlaid web was prepared on acommercial airlaid machine having a width of 66.5 inches. A DanWebairlaid former with two forming heads was used to produce substrateshaving basis weights of about 60 gsm. Weyerhaeuser CF405 bleachedsoftwood kraft fiber in pulp sheet form was used and fiberized in ahammermill, then formed into an airlaid web on a moving wire at a speedof 200 to 300 feet per minute. The newly formed web was densified byheated compaction rolls and transferred to a second wire, where the webwas humidified with an atomized spray of water applying an estimated 5%moisture add on level immediately prior to a second heated compactionroll to further densify the web. The web was then transferred to an ovenwire and sprayed on the top side with ion-sensitive polymer formulationmixture on the exposed surface of the web, applying 10% ion-sensitivepolymer formulation solids relative to the dry fiber mass of the web.

[0230] The ion-sensitive polymer formulation mixture comprised water asthe carrier with 12% binder solids, wherein the binder comprised 75%SSB-4 as the ion-sensitive polymer formulation and 25% Rhoplex® NW-1715Klatex emulsion (Rohm and Haas Corp.) as the co-binder polymer.

[0231] Spray was applied with a series of Quick Veejet® nozzles, NozzleNo. 730077, manufactured by Spraying Systems Co. (Wheaton, Ill.),operating at 95 psi. A spray boom over the web provided 13 such nozzleson 5.5-inch centers with a tip-to-wire distance of 8 inches. Thisarrangement yields 100% overlap of spray cones for the ion-sensitivepolymer formulation solution of this trial.

[0232] After the web was sprayed, it was carried into an oven withthrough-flow of air at about 225° C. to dry the binder solution. The webthen was transferred onto the underside of another oven wire, upon whichit passed over another spray boom where more ion-sensitive polymerformulation solution was applied to the bottom side of the web to addanother 10 weight percent solids relative to the dry fiber mass of theweb. The web then passed through two successive dryer units wherethrough-air drying with air at about 225° C. completed drying of theweb. The pressure differential across the web was approximately 10inches of water. The length of the three dryer sections, from first tothird, respectively, was about 9, 10, and 6 feet.

[0233] The thickness of the web after drying was 1.14 mm (this number,like other physical properties reported here, can vary depending on thefibers, basis weight, and so forth). The machine direction dry tensile(MDDT) strength of the web was measured at 4.59 kg/3 in. The crossdirection dry tensile (CDDT) strength of the web was measured at 3.82kg/3 in with a CD stretch of 8.98%.

[0234] The dried and treated web was then trimmed to 60 inches width,reeled and later slit into 4-inch wide rolls, which were then treatedwith wetting composition and formed into coreless rolls suitable for useas a pre-moistened bath wipe. The wetting composition was sprayeduniformly on one side of the 4-inch wide web prior to reeling the webinto rolls suitably sized for use. The wetting composition was 4 weightpercent NaCl in deionized water.

[0235] The cross direction wet tensile (CDWT) at 4 weight percent salinewas measured at 0.76 kg/3 in. The Soaked CDWT strength was effectively0, as was the Soaked CD Stretch, meaning the sheet was fullydispersible.

EXAMPLE 11

[0236] The sheet formed was identical to that of Example 10 except thatthe fibers in the airlaid web were 75% softwood kraft and 25% PETfibers. The thickness of the web after drying was 1.35 mm. The machinedirection dry tensile (MDDT) strength of the web was measured at 3.87kg/3 in. The cross direction dry tensile (CDDT) strength of the web wasmeasured at 2.84 kg/3 in with a CD stretch of 11.31%. The crossdirection wet tensile (CDWT) at 4% saline was measured at 0.82 kg/3 in.The Soaked CDWT strength was effectively 0, as was the Soaked CDStretch.

EXAMPLE 12

[0237] Additional examples were conducted according to Example 10, withthe exception that Rovene latex emulsion was used as the co-binderpolymer and the basis weight and fiber composition varied as shown inTable 11. The Soaked CDWT results were all 0, indicating a complete lossof tensile strength. Other results are shown in Table 11, where Pulp/PETdesignates the ratio of softwood to synthetic fibers in the substrate,BW is the basis weight in gsm, TH is the thickness in mm, and S-CDWT-Mis the one-hour soak CD wet tensile test for a sample soaked in watercontaining 200 ppm of Ca⁺⁺/Mg⁺⁺ in a 2:1 ratio. TABLE 11 Measurementsfor Examples 3A-3F. Pulp/ Run PET BW TH MDDT CDDT CDWT S-CDWT-M 3A100/0  60.3 1.18 5.44 4.12 0.69 0 3B 85/15 62.9 1.25 4.68 4.23 0.66 0 3C75/25 55.6 1.04 5.48 4.06 0.66 0 3D 75/25 59.3 1.19 4.87 3.96 0.81 0.173E 75/25 60.7 1.48 4.41 3.51 0.79 0.12 3F 85/15 62.7 1.46 4.6 3.82 0.760

[0238] The non-zero S-CDWT-M values (soaked wet tensile in hard water)are non-zero for two trials with 25% PET fibers, suggesting that higheramounts of synthetic fibers can begin to compromise waterdispersibility.

EXAMPLE 13

[0239] A pre-moistened wipe was made similar to that of Example 10,except that the co-binder polymer was a modified Elite® latex emulsionsubstantially free of crosslinking agents provided by National Starch.The basis weight of the web was 61.35, the thickness 1.21 mm, the MDDT5.09 kg/3-in, the MD stretch 7.89%, the CDDT 3.90 kg/3-in, the CDstretch 9.50%, the CDWT in 4% saline 0.78 kg/3-in, the CDWT stretch32.96%, and the residual strengths after one hour in both deionizedwater (S-CDWT) and hard water (S-CDWT-M) were 0 kg/3-in.

EXAMPLE 14 Particulate Addition

[0240] Pre-moistened wipes comprising the basesheet of Example 10 wereprepared with a wetting composition comprising a slurry of particles.The particles were selected from the following products marketed byPresperse, Inc. (Piscataway, N.J.): TABLE 12 Particles from Presperse,Inc. selected for use in pre-moistened wipes Name CompositionCharacteristics MCP-45 Mica and polymethyl Fine powder, platelets coatedwith methacrylate microspheres, 13-17 microns Sericite 98% mica, 2%methicone Fine white powder, hydrophobic SL-012 surface, 2-10 micronsRose talc Talc White powder, 10-12 microns Permethyl Iso-octahexacontane104A (polyisobutene) Cashmir Mica (97%), silica beads Fine white powder,platelets K-II (3%), 0.3 microns coated with microspheres, 10-14 micronsSynthecite Synthetic fluorphogopite Fine powder, 10-15 microns FNK-100Ganzpearl Methyl methacrylate Spherical powder, 4.5-8.5 microns GMX-crosspolymer 0610 Ganzpearl Styrene/divinylbenzene White powder, 4.5-8.5microns GS-0605 copolymer Ganzpearl Styrene/divinylbenzene 0.4 micronsPS-8F copolymer Spheron Amorphous silica White powder, 2-15 microns, lowN-2000 oil absorption Spheron Amorphous silica White powder, 3-15microns, high L-1500 oil absorption

[0241] For each particle type in Table 12, five 1000-gram batches ofwetting composition were prepared with particle concentrations of 0.5%,1%, 2%, 5%, and 10% by weight. Each batch was prepared by adding theappropriate amount of deionized, filtered water to a 1.15-liter beaker(for the 5 batches, the water amounts were, respectively, 926.3 g, 921.3g, 911 g, 881 g, and 831 g). A 2.5-inch magnetic stirring rod stirredthe contents of the jar while residing on a Thermolyne Cimarec 2stirrer, with stirring speed set to maximum to provide a strong centralvortex in each of 5 jars. Each batch comprised 4 weight percent sodiumchloride, added to the water as 40 g of salt; 1 weight percent (10 g)Amisoft ECS22-P acylglutamate surfactant (Ajinomoto, Tokyo, Japan); 0.5weight percent (5 g) DC silicone emulsion (Dow Coming) added to the saltwater and surfactant; 1 weight percent (10 g) Mackstat H 66 preservative(McIntyre Group, Chicago, Ill.); and 0.05 weight percent (0.5 g) offragrance first mixed into 0.25 weight percent (2.5 g) of polysorbate20, then mixed into the solution comprising the previous ingredients;and the respective amount of powder (from 0.5 to 10, weight percent orfrom 5 g to 100 g). The powder was added to the solution as it was beingstirred and allowed to wet and become suspended over a period of about30 minutes after addition of the powder. Some additional stirring byhand was needed for some of the powders to promote mixing. Once thepowder was dispersed in the liquid, the pH was adjusted to 5.0 by addingmalic acid, prepared at a strength of 50 weight percent in water. The pHwas measured with a Cole Parmer Model 59002-00 pH/mV/° C. meter, with aModel 59002-72 KK8 electrode.

[0242] Each of the particle suspensions was then added to dried airlaidbasesheets that had been treated with NaAMPS binder and a co-binderpolymer according to Example 13. The add level was 200%, withapplication by spray on one side of the web. The moistened web was thensealed in plastic to sit overnight. Examination of the pre-moistenedwipes treated with particulate suspensions as the wetting compositionrevealed that the particles generally remained in the wet wipe withoutthe need for additional thickeners or polymeric retention aids.Squeezing the pre-moistened wipes, for example, yielded a mostly clearfluid apparently substantially devoid of particulates, in contrast tothe milky suspensions used to wet the wipes. Generally, no visibleresidue appeared to be left of the hands after using the wipes. Theparticulates also generally improved opacity and appeared to slightlyprovide tactile property improvements (reduced tack, better Theologicalfeel).

EXAMPLE 15

[0243] The role of ungelled starch particles in the wetting compositionof the present invention was investigated as a means of reducingtackiness and improving surface feel for a pre-moistened wipe. Fivewetting compositions containing tapioca starch were prepared accordingto the formulations in Table 13. Softwood airlaid webs according toExample 10 were wetted with the wetting composition with a 300% add-onlevel. (QS means “quantity sufficient” to achieve the desired pH). TABLE13 Formulations for five wetting compositions containing starch WaterPhase A B C D E Water (Tap) 76.9 71.9 68.9 66.9 96.45 Laponite XLS 2 2 22 Phospholipid CDM 0.5 Malic Acid (50% 7 7 7 7 Solution) to pH 4 Tapioca28-1810 10 15 18 20 DC 1784 1 1 1 1 Dragoco Fragrance 0.1 0.1 0.1 0.10.05 0/708768 Mackstate H 66 0.5 0.5 0.5 0.5 0.5 Sodium Chloride 1.5 1.51.5 1.5 1.5 Mackam 2C 1 1 1 1 1 Malic Acid (50% QS QS QS QS QS Solution)to pH 4

[0244] The pre-moistened wipes comprising starch displayed reducedtackiness when handled with the human hand than did similarpre-moistened wipes without the starch. The wipes containing starch alsofelt smoother.

EXAMPLE 16

[0245] Additional pre-moistened wipes were prepared using the wettingcompositions displayed in Table 14, one of which comprised starch as anadditive and the other which comprised botanicals. The wettingcomposition was added to an airlaid fibrous substrate comprising anion-sensitive binder. The wetting composition was added at add-on levelsof 300 and 200 weight percent, respectively. TABLE 14 Formulations fortwo wetting compositions Code Starch Botanical formula # 1  2 RawMaterials Water Phase Water (Tap) 61.4 95.45 Laponite XLS 2 PhospholipidCDM 0.5 Malic Acid (50% 7 Solution) to pH 4 Tapioca 28-1810 25 DC 1784 10.5 Dragoco Fragrance 0.1 0.05 0/708768 Mackstate H 66 1 0.5 SodiumChloride 1.5 1.5 Mackam 2C 1 Malic Acid (50% Solution) QS QS to pH 4CS-22 0.5 Emulgin G 0.5 Witch Hazel 0.5 100    100    pH- Final Solutionadd-on 300% 200%

EXAMPLE 17 Binder Specifications

[0246] A variety of ion-sensitive binders were prepared comprisingacrylic acid (AA), butacrylic acid (BA), 2-ethylhexyl-acrylic acid, andAMPS, with the mole percents and molecular weights shown in Table 15:TABLE 15 Ion-sensitive binders comprising AMPS SSB Mole percent ofmonomers: Code MW × 10⁻⁶ AA BA 2-EHA AMPS A 1.54 60 24.5 10.5 5 B 1.3260 24.5 10.5 5 C 0.604 60 24.5 10.5 5 D 0.548 60 24.5 10.5 5 E 0.609 6024.5 10.5 5 F 0.545 60 24.5 10.5 5 G 1.21 62 24.5 8.5 5 H 0.79 60 24.510.5 5 I 0.916 60 24.5 10.5 5 J 0.71 60 24.5 10.5 5 K 0.786 60 24.5 10.55 L 0.845 60 24.5 10.5 5 M 0.640 60 24.5 10.5 5 N 0.800 60 24.5 10.5 5 O0.635 60 24.5 10.5 5 P 0.610 60 24.5 10.5 5 Q 0.575 60 24.5 10.5 5 R0.638 60 24.5 10.5 5 S 0.912 62 26.5 7.5 4 T 0.609 60 25.5 10.5 4 U0.835 58 27 10 5 V 0.675 58 27 10 5 W 0.734 58 27 10 5 X 0.716 58 27 105 Y 0.650 58 27 10 5 Z 0.718 58 27 10 5 AA 0.518 58 27 10 5 AB 0.544 5827 10 5

[0247] These binders were prepared according to the methods of Example1, but scaled up as a batch process capable of producing several hundredgallons per batch.

EXAMPLE 18 Typical Wetting Solution

[0248] A wetting composition was prepared by combining the followingingredients according to the specific weight percent: 92.88 weightpercent deionized water, 4 weight percent NaCl, 1 weight percentMackstat H-66 preservative (McIntyre Group, Chicago, Ill.), 1 weightpercent CS22 acyl glutamate anionic surfactant (Amisoft Corp., Tokyo,Japan), 0.5 weight percent DC₁₇₈₅ silicone emulsion (Dow Coming), 0.25weight percent Solulan L-575 (PEG-75 lanolin, available from Amerchol, adivision of Union Carbide), 0.05 weight percent Dragoco fragrance0/708768 (Dragoco S A, Cuautitlán Izcalli, D. F. Mexico, Mexico), 0.25weight percent polysorbate 20, and about 0.07 weight percent of 50percent by weight malic acid solution to bring the pH to 5.0.

EXAMPLE 19 A Treated Substrate

[0249] An airlaid substrate was made with the equipment described forExample 10. Basis weight was 65 gsm and the fibers were 100%Weyerhaeuser CF405 bleached softwood kraft pulp. The binder solution had12.8 weight percent binder solids, 75 weight percent of which was SSBCode H of Table 15 and 25 weight percent Dur-O-Set RB latex co-binder(National Starch). The binder solution was sprayed onto the web asdescribed in Example 1, with the dryer air temperature at 215° C. forall three oven sections.

EXAMPLE 20 A Treated Substrate

[0250] An airlaid substrate was made according to Example 10, exceptthat the basis weight was 63 gsm and the oven temperature was 227° C.Reel speed was 197 fpm. Thickness of the dried web was 1.30 mm.

[0251] MDDT was 5.55 kg/3-in, CCDT was 4.83 kg/3-in, CDWT (in 4% NaClsolution) was 1.07 kg/3-in, and S-CDWT as well as S-CDWT-M (1 hour soaktests) gave 0 kg/3-in.

[0252] Some of the dried web was slit to a 4.25-inch width and treatedwith wetting composition at 225% add-on, comprising 4% NaCl in deionizedwater without surfactant. The moistened web was perforated with aperf-knife operating with a depth of 0.070 inches to perforate every 4.5inches. The perforated web was rolled into a coreless roll with 100perforated sheets per roll (approximately 37.5 feet per roll) and placedin a white plastic cartridge for subsequent use in a dispenser forpre-moistened wipes.

EXAMPLE 21

[0253] A portion of the dried, treated web of Example 20 was wetted withthe wetting composition of Example 18 and converted into perforate rollform for use as pre-moistened wipes to be dispensed from a bathroomdispenser.

COMPARATIVE EXAMPLE 22

[0254] A conventional, adhesively bonded airlaid substrate with a basisweight of 60.1 gsm was created using the methods described in Example10. Dur-O-Set E-646 (National Starch) was used with wood pulp (CF405)The substrate was wetted with a 4% NaCl solution and tested using themethods described. The binder was entirely the self-crosslinkingDur-O-Set E-646 compound; no salt-sensitive binder was applied. Thebinder solids mass was 17% of the substrate mass. Dry thickness of theweb was 1.4 mm, and the CDWT value was 1.3 kg/3-in, while S-CDWT was 1.2kg and S-CDWT-M was 1.15 kg, indicating that the web maintained nearlyall of its strength after soaking, and suggesting that the crosslinkedlatex provided the majority of the tensile strength of the web and thatthe latex bonds did not weaken substantially in water.

EXAMPLE 23

[0255] A variety of binder/co-binder combinations were prepared, asdescribed below, using the salt-sensitive binders of Table 15 andco-binders as shown in Table 16 which are not self-crosslinkable. TABLE16 Latex co-binders that are not self-crosslinkable. Co-binder IDCo-binder Manufacturer 1 Dur-O-Set RB National Starch 2 Rhoplex NW-1715KRohm and Haas 3 Rovene 4817 Mallard Creek

[0256] Using the methods described in Example 10, airlaid substrateswere made from bleached kraft fibers. The substrate was wetted with a 4%NaCl solution and tested using the methods described. All substrateswere comprised of wood pulp (CF405) and binder. Results are shown inTable 17, where the binder mixture consistently comprised 75% of asalt-sensitive binder selected from Table 15 and 25% of a co-binderselected from Table 16. The binder/co-binder column refers to the binderand co-binders listed in Table 15 and 16, respectively. For example,“A/1” refers to a mixture of SSB Code A in Table 15 and co-binder 1 ofTable 16. TABLE 17 Tensile data for various binder systems. SSBS-CDWT-M3 % Binder/ MW × BW Thick CDWT S-CDWT S-CDWT-M 3 hrs Binder Cob.10⁻⁶ (gsm) (mm) (kg/3″) (kg/3″) (kg/3″) (kg/3″) 16.7 A/1 1.54 71.3 1.460.990 0 0.330 0.180 20 B/1 1.32 63.3 1.25 1.242 0.163 0.470 0.310 20 B/11.32 66.6 1.46 1.040 0 0.230 0.550 20 G/1 1.21 62.2 1.20 1.002 0 0.270 020 H/1 0.79 63.1 1.3 1.070 0 0 0 16.7 C/1 0.604 73.6 1.59 0.750 0 0 0 20C/1 0.604 71.2 1.5 0.900 0 0 0 20 C/1 0.604 61.1 1.28 1.140 0 0 0 20 D/10.548 62.5 1.32 0.900 0 0 0

[0257] As seen in Table 17, nearly all of the substrates have lost morethat 80% of their tensile strength after soaking in deionized water for1 hour (S-CDWT). The substrates have lost more that 60% of theirstrength (S-CDWT-M) after soaking for 1 hour in a solution of 200 ppm ofdivalent cations (Ca++/Mg++ 2:1). In particular, for the runs shown inTable 17, the samples completely lost their strength in 1 hour in the200 ppm solution when the molecular weight of the salt sensitive binderwas less than 1,200,000. After 3 hours of soak time in the 200 ppmdivalent cation solution, the SSBs with high molecular weight havegenerally lost more of their strength, but may still have non-zerotensile strength.

[0258] By comparison, the comparative Example 22 lost less than 15% ofits strength after soaking for 1 hour in either deionized water or 200ppm divalent ion solution. All of the substrates in Table 17 lost moretensile strength on soaking than the comparative Example 22.

EXAMPLE 24

[0259] Different co-binders from Table 16 were blended with thesalt-sensitive binder Code F from Table 15. The binder blend was thenapplied using the methods described in Example 10 to create the airlaidsubstrates listed in Table 18. In each case, 20% binder solids wereapplied to the substrate in a blend of 75% SSB/25% co-binder TABLE 18Tensile data for various co-binder systems. Co- Binder/ binder BW Thick,CDWT S-CDWT S-CDWT-M Co-binder Used (gsm) (mm) (kg/3″) (kg/3″) (kg/3″)F/1 Dur-O- 59.77 1.06 0.735 0 0 Set RB F/2 Rhoplex 60.83 1.14 0.758 0 0F/3 Rovene 60.28 1.18 0.687 0 0

[0260] Under similar run conditions, all three co-binders performcomparably. All of the substrates have lost their tensile strength(S-CDWT-M) in the 200 ppm divalent cation solution independent ofco-binder type.

EXAMPLE 25

[0261] Measurements were made of the peel force required to unroll theproduct from the outer layers of a coreless roll of pre-moistened wipessuitable for use as a moist toilet paper product. The product was madeaccording to Example 10 with an add-on level of 200% wettingcomposition. The dried web was slit to a 4.25-inch width and treatedwith wetting composition at 200% add-on, comprising 4% NaCl in deionizedwater with surfactants, silicone, and lanolin as listed in Table 19 forwetting composition Q, R, and S. The moistened web was perforated with aperf-knife operating to perforate every 4.5 inches. The perforated webwas rolled into a coreless roll with 100 perforated sheets per roll(approximately 37.5 feet per roll) and sealed in a plastic cartridge forsubsequent use in a dispenser for pre-moistened wipes. TABLE 19 Otheradditives in three wetting compositions. Silicone Acylglutamate Solutionemulsion Lanolin surfactant Q 0.50% 0.25% CS22 R 1.00% 0.25% ECS 22P S1.00%   0% ECS 22P

[0262] The roll rested freely in a plastic tub with a rounded, ribbedbottom that held the roll in place with a minimum of friction when theroll was unwound by pulling vertically upwards on the tail end of theroll. Adjacent plies adhered to each other such that some force wasrequired to separate the layers. The peel force needed was less than theweight of the roll and appeared to be substantially greater than thefrictional resistance offered by the tub as the roll turned, evidencedin part by angle between the web and the roll at the point ofseparation. With no peel force, the angle between the web being pulledup and a line normal to the roll at the point of separation would be 90degrees, but in unwinding the moist roll with the salt-sensitive binder,the angle was substantially less than 90 degrees, thus imparting peelforce to separate the web.

[0263] The peel force was measured with an MTS Sintech 1/G test machinewith TestWorks 3.10 software. All testing as done in a conditionedlaboratory under Tappi Standard conditions. A 4.5-inch wide clamp withrubber surfaces gripped the tail of a roll, with the roll positiondirectly underneath the clamp such the tail would remain vertical as itwas unwound from the roll if there were no peel force causing the web towrap a portion of the roll and deflect from the vertical. The clamp wasattached to the crosshead, which pulled the tissue web upward at a speedof 100 cm/minute. Peel force was measured by a 50 N load cell. Theaverage load to pull 18 sheets away from the roll was recorded byaveraging two runs in which 4 sheets each were separated and two runs inwhich 5 sheets each were separated. Only the first 18 sheets from theroll were used in the measurement. The average peel force for two rollsper condition (for an overall average taken over a total of 36 sheets)is reported in Table 20 below. TABLE 20 Peel force in grams to remove aweb from a wound moist roll. Thickness, Binder MDWT, Peel force, BW, gsmmm add-on Solution g/in g 65 1.1 22% Q 500 167 65 1.1 22% R 475 170 651.1 22% S 533 162 60 0.76 20% Q 438 131 55 0.76 20% Q 353 106 55 0.7620% R 341 120 55 0.84 20% R 385 115

[0264] Peel forces for a roll having a width between 7 and 15 cm (thewidth of the rolls tested in Table 20 are 10.8 cm) are desirably areless than 500 g, more specifically less than 300 g, more specificallyless than about 200 g, more specifically still less than about 160 g,most specifically less than about 120 g, with an exemplary range of fromabout 50 g to about 350 g, or from about 80 g to about 200 g. Moregenerally, the peel force per 4-inch width of a moist roll can be any ofthe aforementioned values of ranges.

EXAMPLE 26

[0265] Additional samples were prepared according to Example 24 above,except that 15 weight % of the fiber blend consisted of 6-mm, crimpedPET fibers (KoSa). Different co-binders from Table 16 were blended withthe salt-sensitive binder Code F from Table 15. The binder blend wasthen applied using the methods described in Example 10 to create theairlaid substrates whose properties are listed in Table 21. In eachcase, 20% binder solids were applied to the substrate in a blend of 75%SSB/25% co-binder. The properties of these substrates were measuredafter wetting with a 4% NaCl solution. All three co-binders performcomparably. All of the substrates have lost their tensile strength in200 ppm divalent cation solution independent of co-binder type. Comparedto the parallel results in Example 24, incorporation of the syntheticfibers impart a slight to modest strength improvement (CDWT) and amodest increase in dry bulk. TABLE 21 Data for substrates with PETfibers and various co-binders. Co- Binder/ binder BW Thick, CDWT S-CDWTS-CDWT-M Co-binder Used (gsm) (mm) (kg/3″) (kg/3″) (kg/3″) F/1 Dur-O-63.32 1.31 0.782 0 0 Set RB F/2 Rhoplex 62.07 1.35 0.820 0 0 F/3 Rovene62.90 1.25 0.660 0 0

EXAMPLE 27

[0266] Additional examples were conducted according to Example 26 withincreasing amounts of synthetic fiber being added to the fiber blend.

[0267] Either a 6 mm crimped PET fiber (KoSa) or a 6 mm, crimped 2.4dtex, Lyocell fiber was used as noted in Table 22 below. The binderblend was a constant blend of 75% SSB and 25% co-binder. TABLE 22 Datafor substrates with PET fibers and various co-binders. Pulp/ Synth.Binder Binder/ BW Thick. CDWT S-CDWT S-CDWT-M Synth. Type % Co-binder(gsm) (mm) (kg/3″) (kg/3″) (kg/3″) 100/0  None 20% F/3 60.28 1.18 0.6870 0 85/15 PET 20% F/3 62.90 1.25 0.660 0 0 6 mm 75/25 PET 20% F/3 59.321.19 0.805 0 0.170 6 mm 75/25 PET 20% F/3 60.65 1.48 0.790 0 0.120 6 mm85/15 PET 20% F/3 62.67 1.46 0.757 0 0 6 mm 85/15 Lyocell- 19% E/2 58.31.08 0.969 0 0 6 mm 75/25 Lyocell- 19% E/2 59.2 1.09 1.080 0 0.127 6 mm

[0268] The non-zero soaked CDWT tensiles in 200 ppm of divalent cationare non-zero for those trial combinations with 25% synthetic fiber (PETor Lyocell), suggesting that higher amounts can begin to compromisewater dispersibility.

EXAMPLE 28

[0269] The substrates shown in Table 23 were all made according to themethods of Example 10 and prepared according to the methods described inExample 23. All of the substrates in Table 23 were formed from airlaidpulp (CF405). All binder blends were 75% SSB and 25% co-binder. The drythickness of the sheet was controlled by adjusting the level of webcompaction by the two compaction rolls prior to the first sprayapplication of binder. SSB Codes O and Q from Table 15 were used. TABLE23 Data for substrates with PET fibers and various co-binders. % BinderBinder/ BW Thick. CDWT S-CDWT S-CDWT-M in sheet Cob. (gsm) (mm) (kg/3″)(kg/3″) (kg/3″) 20 O/1 66.0 1.27 1.055 0 0 20 O/1 68.2 0.77 1.550 0 0 20O/1 52.5 1.19 0.728 0 0 20 Q/1 54.19 0.75 1.372 0 0 17 Q/1 57.5 0.891.110 0 0 20 Q/1 59.90 0.75 1.583 0 0 20 Q/1 65.36 0.76 1.696 0 0 20 Q/166.43 1.20 1.296 0 0

[0270] It appears that compaction of the dry web prior to binderapplication can significantly increase final sheet wet strength withoutsacrificing dispersibility. This unexpected level of strength increasecan allow equivalent wet tensiles to be achieved in a variety ofcombinations including basis weight reduction and/or percent binder insheet reductions.

EXAMPLE 29

[0271] All substrates were prepared according to the methods describedin Example 27. All substrates were comprised of the fiber blend noted inTable 24 with 20% binder in the sheet and Dur-O-Set RB serving as theco-binder. Synthetic fibers were crimped and either 6 mm PET (KoSa) or 6or 8 mm Lyocell with 1.7 or 2.4 dtex (Accordis). TABLE 24 Data forsubstrates with various fibers and binders. % Syn. Syn. Binder/ SSB BWThick. CDWT S-CDWT S-CDWT-M Code Fiber Fiber Cob. MW (gsm) (mm) (kg/3″)(kg/3″) (kg/3″) 2701 0 none F/1 545000 59.8 1.06 0.735 0 0 2702 15 PETF/1 545000 63.3 1.31 0.782 0 0 2713 15 L-2.4-6 F/1 545000 62.0 1.390.840 0 0 2714 15 L-1.7-6 F/1 545000 61.8 1.33 0.768 0 0 2715 15 L-1.7-8F/1 545000 63.7 1.47 0.842 0 0 2716 0 none J/1 710000 65.5 1.11 1.193 00 2717 15 L-1.7-8 J/1 710000 61.4 1.02 1.512 0 0.200 3010 0 none R/1638000 61.10 0.80 1.710 0 0 3015 15 PET R/1 638000 62.23 0.86 1.769 00.070 3016 5 L-1.7-8 R/1 638000 60.63 0.79 2.620 0 0.170

[0272] The examples of Table 24 suggest that that synthetic fiberlength, SSB molecular weight and web compaction in combination canaffect the dispersibility of the product as indicated by its S-CDWT-Mvalue. All substrates comprised of the 6 or 8 mm synthetic fibers weredispersible with the lower molecular weight SSB. As the molecular weightwas increased, the 8 mm Lyocell substrate began to retain some of itsstrength after soaking for 1 hour in the divalent cation solution; thissubstrate, however, was dispersible in DI water. Densifying the dry webprior to binder application can also impact the dispersibility of asynthetic fiber containing substrate (Codes 3015 and 3016). Both Code3015 and Code 3016 were fully dispersible in the DI water. Sheetdispersibility can be managed by choosing lower molecular weight SSBs incombination with synthetic fibers and dry web densification.

EXAMPLE 30

[0273] The substrates listed in Table 25 were prepared, wetted with 4%NaCl solution, and tested according to the methods described in Example29. Each substrate was comprised of the fiber blend noted and 20% binderwith the SSB/co-binder blend noted in Table 25. Dur-O-Set RB was theco-binder used in all of the samples listed in Table 25. All codes used100% softwood fiber except the last one, Code 2813, which comprised 15%PET fiber (the 6 mm, crimped fiber obtained from KoSa). Basis weight wasgenerally held constant to about 60 gsm. The thickness of the airlaidweb was controlled by adjusting the level of web compaction by the twocompaction rolls prior to the first spray application of binder. The dryCD stiffness of selected substrates in Table 25 were measured using aHandle-o-meter and reported as stiffness. TABLE 25 Data for substrateswith various binder blends. Code Binder/Cob. Bind. Type BW (gsm) Thick.(mm) CDWT (kg/3″) S-CDWT (kg/3″) S-CDWT-M (kg/3″) Stiffness g force 3025100/0  R 58.42 1.23 1.003 0 0 200 3026 100/0  R 58.68 0.76 1.953 0 0 2143007 75/25 R 60.23 1.19 0.942 0 0 189 3008 75/25 R 59.38 1.03 1.161 0 03009 75/25 R 59.73 0.92 1.243 0 0 3010 75/25 R 61.10 0.80 1.713 0 0 1813021 65/35 R 62.24 1.17 0.988 0 0.050 177 3022 65/35 R 62.07 0.81 1.8000.030 0.200 167 3024 55/45 R 58.95 1.23 0.853 0 0.100 145 3023 55/45 R59.01 0.78 1.608 0.150 0.230 141 2812 65/35 P 59.1 1.37 0.735 0 0 281365/35 P 59.4 1.41 0.723 0 0

[0274] As the percentage of the salt sensitive binder in the blend isdecreased from 100% to 55% there is only to modest decrease in the CDWTat constant dry bulk. At compositions of 65% salt-sensitive binder inthe binder blend, the substrate begins to retain a greater portion ofits wet strength after soaking for 1 hour in 200 ppm of the divalentcation solution. As the web is densified prior to the first binderapplication and the percentage of salt sensitive binder in the blend isreduced to 65% or lower, a greater amount of strength is retained aftersoaking in DI water or the 200 ppm divalent cation solution for 1 hourcompared to the same compositions at a higher dry bulk. These examplessuggest that increasing the co-binder content with or without additionaldensification of the web can begin to compromise substratedispersibility.

[0275] The results in Table 25 also show significant CDWT increases asthe thickness of the dry web is compressed prior to the application ofthe binder. Codes 3007 to 3010 show that the CDWT is increasing as afunction of decreasing dry bulk with no loss of substrate dispersibilityat constant binder conditions.

[0276] Based on the Handle-O-Meter results (stiffness), it appears thatas the percentage of salt sensitive binder in the blend is decreased,the CD stiffness of the substrate decreases.

EXAMPLE 31

[0277] The substrates listed in Table 26 were prepared according to themethod described in Examples 10 and 23. Each substrate comprised pulp(CF405) and 20% binder. The binder had the SSB/co-binder blend given inTable 26. Dur-O-Set RB was the co-binder. The substrate was convertedinto roll form and wetted with solution Q of Table 19 (solution D).Measurements were made of the peel force required to unroll the productfrom the outer layers of the coreless roll of pre-moistened wipesaccording to the method described in Example 25. The results of thesetests are recorded in Table 26 below. TABLE 26 Peel force results forcoreless rolls. % Binder Binder Binder/ BW Thick. Peel Code In sheetBlend Cob. (gsm) (mm) (g) 3026 20 100/0  R/1 58.68 0.76 142 3010 2075/25 R/1 61.10 0.80 139 3022 20 65/35 R/1 62.07 0.81 116 3023 20 55/45R/1 59.01 0.78 111

[0278] In this case, decreasing the percentage of the salt-sensitivebinder in the blend decreased the peel force.

EXAMPLE 32

[0279] Samples were made as in Example 10 using 75/25 blends of SSbbinder (see Table 15) and Dur-O-Set RB co-binder (co-binder 1 of Table16), according to the information in Table 27 below. Tensile results inTable 27 show good dispersibility over a range of product conditions.TABLE 27 Tensile results for a range of binders and basesheetproperties. % Binder Binder/Cob. SSB MW BW (gsm) Thick. (mm) CDWT(kg/3″) S-CDWT (kg/3″) S-CDWT-M (kg/3″) 20 O/1 632000 52.5 1.19 0728 0 020 Q/1 575000 54.19 0.75 1.372 0 0 15.2 J/1 710000 55.2 1.47 0.320 0 024 L/1 834000 60.4 0.92 1.070 0 0 20 D/1 548000 62.5 1.32 0.900 0 0 20H/1 790000 63.1 1.3 1.070 0 0 22 R/1 638000 66.47 0.76 2.273 0 0 20 C/1604,000 74.4 1.47 1.120 0 0

[0280] The samples reported in Table 27 demonstrate some of the rangesof binder content, basis weight, and web thickness over whichdispersible substrates can be made.

EXAMPLE 33

[0281] Samples were made generally as in Example 10 using 75/25 blendsof SSB binder (see Table 15) and co-binder (see Table 16) as noted inTable 28. All substrates contain 6 mm crimped, 2.4 dtex Lyocell(Accordis) as 15% of the fiber blend with 85% softwood pulp (CF405). Allsubstrates are comprised of 19% binder and 81% of the binder blend.TABLE 28 Tensile results for a range of binders and basesheetproperties. Binder/ SSB BW Thick. CDWT S-CDWT S-CDWT-M Cob. MW. (gsm)(mm) (kg/3″) (kg/3″) (kg/3″) L/1 845,000 61.1 1.17 0.960 0 0 W/1 734,00060.2 1.17 0.960 0 0.198 AB/1 544,000 56.2 0.95 1.060 0 0 AB/2 544,00058.6 1.06 0.990 0 0.205 E/2 609,000 58.3 1.08 0.969 0 0

[0282] In Table 28, all samples lost at least 75% of their wet strengthafter soaking in the 200 ppm divalent cation solution for 1 hour(S-CDWT-M). The main differences in these samples is in the SSBcomposition, as depicted in Table 15. Salt-sensitive binders L and Ehave the same composition, but different molecular weights, than thesalt sensitive binders W and AB (see Table 15). Salt sensitive binders Wand AB have the same composition but different molecular weights. TheW/1- and AB/2-treated substrates appear to be less dispersible than theL/1- and E/2-treated substrates independently of co-binder. Reducing thesalt sensitive binder's molecular weight can be used to make thesubstrate more dispersible as is shown by substrate AB/1. Or, changingthe salt sensitive binder's composition can be used to make thesubstrate more dispersible as demonstrated by L/1 and E/2. Thus, bymodifying the salt sensitive binder's molecular composition or itsmolecular weight, fully dispersible blends can be made. Alternatively,by selecting a different co-binder chemistry to be more compatible withthe salt sensitive binder, fully dispersible binder blends can be madeas demonstrated by substrates AB/2 and AB/1.

EXAMPLE 34

[0283] A latex emulsion comprising about 6% NMA crosslinker, AirFlex 105(Air Products, Allentown, Pa.), was combined with SSB Code H of Table 15at a ratio of 75 parts SSB to 25 parts latex solids and cast into 8 barswith dimensions 1 cm×4 cm×3 mm as described in Example 9. Four bars wereprepared by drying in air at 60° C. overnight, while the other four barswere dried at 167° C. for 3 hours. Two bars from each set were then eachplaced in 30 ml of 4% NaCl solution and allowed to sit for one hour,after which solubility was determined gravimetrically. Bars from bothsets (the two drying conditions) were essentially completely insolublein the saline solution. The remaining bars from each set were eachplaced in 30 ml of hard water containing 200 ppm calcium and magnesiumions at a 2:1 ratio at about 23° C. and allowed to sit for one hour. Thetwo bars dried at 167° C. and placed in hard water were essentiallycompletely insoluble (0% soluble). The two bars dried at 60° C. andplaced in hard water were 54% and 53% soluble, respectively, which wasunexpectedly low given that the latex should be substantiallyuncrosslinked for drying at this temperature. However, some coagulationoccurred when the latex was mixed with the SSB, suggesting a possiblecompatibility problem between the two mixtures, and thus solubility maybe impaired, or some coagulated particles may not have passed throughthe filter paper. It is also possible that some of the NMA crosslinkerin the Airflex latex may have promoted crosslinking or gelling of theblend. While it is believed that a more compatible latex emulsion wouldhave yielded higher solubility, it is also believed that co-binders thatare relatively low in crosslinking agents (e.g., less than 6%,specifically less than 2%, more specifically less than 1%, and mostspecifically less than 0.3% crosslinker on a solids mass basis) can behelpful in maintaining high solubility of the dried polymer blend.

[0284]FIG. 1 shows the wet tensile results for treated airlaidbasesheets, wherein the tests have been carried out in different salinesolutions or hard water. The airlaid basesheets were prepared accordingto Example 10 and provided with 20% add-on of salt-sensitive bindercompositions labeled as Code X, Code Y, and Code Z. Code X is a binderpolymer comprising 60% acrylic acid, 10.5% 2-ethylhexyl acrylate, 24.5%butyl acrylate, and 5% NaAMPS, polymerized according to Example 1 with amolecular weight of 1.3 million, corresponding to Code B in Table 15.Code Y is similar but with a molecular weight of about 550,000,corresponding to Code D in Table 15. Code Z is similar but has 62%acrylic acid and 8.5% 2-ethylhexyl acrylate as monomers, with amolecular weight of about 1.2 million, corresponding to Code G in Table15. All binders were blended with Dur-O-Set RB co-binder in a 75:25ratio. The treated webs were dried, as in Example 10, and then wettedwith either a 4% or 1.5% NaCl solution. Wet tensile testing wasconducted according to the CDWT protocol with the exceptions describedin Example 5 (e.g., a 1-inch wide strip and a MTS tensile tester wereused).

[0285] Soaked CD tensile tests were conducted on samples prepared withthe 4% solution. The four columns shown for each code (some of which arenot visible due to zero values) correspond to the results from the fourdifferent tests. The first two columns are the CDWT values “as is” forthe web in either the 4% or 1.5% NaCl solution. The third and fourthcolumns are the S-CDWT-M (hard water soak) results at 1 hour and 3 hoursfor each web that had been wetted with the 4% solution.

[0286] The results show good wet strength at both 1.5% NaCl and 4% NaCl,with excellent strength loss for webs treated with Code Y (Hard WaterDispersibility of 100%), good strength loss for Code Z, and residualstrength still present for Code X. Comparison of Code X to Code Ysuggests that a reduction in molecular weight can promote dispersibilityof the salt-sensitive binder.

[0287]FIG. 2 is a chart showing how wet tensile strength (reported asCDWT in grams per 2.54 cm over a range of soak times) can change overtime as 68 gsm softwood airlaid webs comprising ion-sensitive bindersare soaked in solutions comprising calcium ions. The moistened webs wereprepared with 20% binder by weight comprising 85% Lion (Tokyo, Japan)SSB-3b acrylic-acid based terpolymer and 15% Dur-O-Set RB (NationalStarch) co-binder. After being dried, the webs were wetted with asolution containing 0.9% NaCl, 0.5% phospholipid CDM (Mona), and 0.5%Mackstat H-66 and displayed a wet strength of about 400 g/in (or g/2.54cm). Solution add-on was 250% based on the dry weight of the web. Thetreated webs were then soaked in NaCl-free water containing calcium ionsat levels of 0, 13, 29, and 109 ppm, yielding the four curves shown inFIG. 2 for wet tensile strength versus time. At 109 ppm calcium ionsthere is essentially no loss in strength. Strengths over 100 g/in aremaintained in 29 ppm calcium ions. It appears that even a small amountof calcium ions in the water will interfere with a dispersibility of aweb treated with the Lion SSB-3b product.

[0288]FIG. 3 compares two data sets with Lion SSB-3b product taken fromFIG. 2 (labeled as Code 3300) with a sulfonated salt-sensitive binderblended with Dur-O-Set RB polymer in a 75/25 ratio. The data set labeledas Code 2102 refers to a 65-gsm web containing the sulfonatedsalt-sensitive binder, which corresponds to SSB Code H in Table 15. Thisweb was wetted with the solution described in Table 4. Solution add-onwas 225% based on the dry weight of the web. This binder formulationdisplayed a rapid drop in tensile strength—hence goodtriggerability—when immersed in hard water, even at a calcium ionconcentration of 257 ppm. Thus, the sulfonated salt-sensitive binders ofthe present invention show a dramatic improvement in their ability to bedispersible in hard water relative to prior acrylic-acid basedterpolymers.

[0289] Tensile results for data in FIG. 2 and FIG. 3 were obtained withan MTS tensile test devices, the MTS 500/S unit (MTS Systems, ResearchPark, N.C.) using the Testworks™ 3.10 for Windows software. Instead ofthe normal 3-inch strip for testing, a 1-inch wide strip was used, cutto 6 inches in length. The gauge length between the rubber-coated jawsof the test device was 3 inches. Testing was operated at the specifiedcrosshead speed of 12 in/min.

COMPARATIVE EXAMPLE 35

[0290] The attributes of three, commercially available flushable wetwipe products were characterized and are listed in table 100 Theseproducts are Cottonelle® Flushable Moist Wipes, Just for Me™ FlushableMoist Wipes, and Charmin Kid Fresh® Flushable Wipes. All three productsare sold in a flat, folded format. The substrates of these products areall adhesively bonded airlaid basesheets. While these products have thestrength, opacity, thickness, and cup crush values to make themcommercial successful, none of them are dispersible. All three of theseproducts retain nearly all of their CDWT strength on soaking in 10 ppmor 200 ppm Ca++/Mg++ solutions.

COMPARATIVE EXAMPLE 36

[0291] Moist Mates™ is a product that has been introduced into themarket on two different occasions. In its first introduction ahydroentangled basesheet was used to produce a wet wipe with theproperties noted in table 100, coded as MM-1. This product had goodattributes except that it retained a substantial amount of its originalstrength (>100 g/1″) on soaking in either 10 ppm or 200 ppm Ca++/Mg ++solutions.

[0292] In its second introduction to the market, an adhesively bondedairlaid basehsheet was used. The properties of this product also appearin Table 29, coded as MM-2. The second introduction has acceptableproperties except that it is again not dispersible and in fact haspoorer dispersiblity than its original introductory product. The MoistMates™ product is sold in a roll format.

COMPARATIVE EXAMPLE 37

[0293] Merries Flushable Oshirifuki is a Japanese, flushable, baby wipedistributed by Kao Corporation and sold in an inter-folded format. It isa 2-ply product is made from creped wet laid sheets that appear to havebeen embossed together. The product contains pulp fibers andcarboxymethylcellulose. The wetting solution contains water,preservatives, calcium and sodium ions and more than 20% organic solventin the forms of propylene glycol and 1,3 butane diol.

[0294] The properties of this product are listed in Table 29 and codedas Kao. Of all the examples in Table 29, this product has the lowestopacity. Although it has excellent strength and dispersibilityproperties, it relies on the heavy use of organic solvents in thewetting solution to obtain this level of performance.

COMPARATIVE EXAMPLE 38

[0295] Another flushable baby wipe is distributed by Pigeon under thename Flushable Oshiri Nap. This product is made from a very weakhydroentangled basesheet. The sheet is composed of pulp and rayonfibers. The properties of this product are listed in Table 29, coded asPigeon. It is sold as an inter-folded product.

[0296] This product is very weak and difficult to dispense. Pigeon'spackaging warns the consumer that the wipes may tear when pulling themout of the packaging. It represents the lower limit of in use strength.While the product has good thickness, opacity, and cup crush, it remainsnon-dispersible in either 10 ppm or 200 pppm Ca++/Mg++ solutions.

EXAMPLE 39

[0297] Typical Wetting Solution

[0298] A wetting composition was prepared by combining the followingingredients according to the specific weight percent: 93.16 weightpercent deionized water, 4 weight percent Top-Flo Evaporated Salt, 1weight percent Mackstat H-66 preservative (McIntyre Group, Chicago,Ill.), 1 weight percent Sodium Cocoyl Gluatamate anionic surfactant(Hampshire Chemical, Nashua, N.H.), 0.42 weight percent DC-1785 siliconeemulsion (Dow Corning, Midland Mich.), 0.1 weight percent Firmenichfragrance (Firmenich, Inc. Princeton, N.J.) 0.25 weight percentpolysorbate 20, and about 0.07 weight percent of 50 percent by weightmalic acid solution to bring the pH to 5.0.

EXAMPLE 40

[0299] Airlaid substrates 3007 and 3010 from Example 30, Table 25, werewetted with the wetting solution of Example 36 using a hand sprayapplication of the wetting solution. Solution add-on was 200%. Thesamples were immersed in water containing 10 ppm or 200 ppm of Ca++/Mg++in a 2:1 ratio, soaked for 1 hour and then tested.

[0300] Wet tensile results were obtained with an MTS Synergie 200tensile tester using the TestworksTM 3.10 for Windows software. A 1-inchwide by 4-inch long strip was used for testing. The gauge length betweenthe jaws of the test device was 3 inches. Testing was operated at thespecified cross head speed of 12 in/min. The peak load for each of 10samples was measured and the average peak load in g/1″ reported in Table29.

[0301] The wetted sheet thickness, opacity, and cup crush of thesesamples were measured and also recorded in Table 29. Both wet wipes 3007and 3010 have excellent hard water dispersibility with 1 hour soakedCDWTs in water containing the 10 ppm of Ca++/Mg++ less than 30 g/1″.Both wipes have sheet thicknesses greater than 0.3 mm and opacitiesgreater than 35%. Wet wipe 3007 has adequate in use strength at 159g/1″.

EXAMPLE 41

[0302] The properties of the premoistened wipes of Example 21 weremeasured. They are listed in Table 29. These rolled wipes have an in useCD wet tensile >300 g/1″, a sheet thickness >0.3 mm, an opacity greaterthan 35%, a cup crush less than 40 g and excellent hard waterdispersibility.

EXAMPLE 42

[0303] A 65 gsm substrate with 22% binder and a dry sheet thickness of1.1 mm was made according to the methods of Example 10. The binder was a75/25 blend of SSB Q of Table 15 in Example 17 and cobinder 1 of Table16 in Example 23. The substrate was formed using Weyerhauser pulp CF405.Some of the dried web was slit to 4.25-inch width and treated with thewetting solution of example 18 at 225% add-on. The moistened web wasconverted into a coreless, perforated roll form for use as pre-moistenedwipes to be dispensed from a bathroom dispenser. The properties of thesewipes appear in Table 29 listed as Code G.

[0304] Code G has an in use CD wet tensile >300 g/1″, a wet sheetthickness >0.3 mm, an wet opacity greater than 35%, a wet cup crush lessthan 40 g and excellent hard water dispersibility (5% of original in useCDWT). It has CDWTs of less than 30 g/1″ after soaking in waterscontaining either 10 ppm or 200 ppm of a 2:1 Ca++/Mg++.

EXAMPLE 43

[0305] Using the methods of Example 10, both a 60 and a 55 gsm substratewere made with 20% binder and a dry sheet thickness of 0.8 mm. Thebinder was a 75/25 blend of SSB Q of Table 15 in Example 17 and cobinder1 of Table 16 in Example 23. Weyerhauser pulp CF-405 was used. Some ofeach of the dried webs were slit to 4.25-inch width and treated with thewetting solution of example 18 at 225% add-on. Each moistened web wasconverted into a coreless, perforated roll form for use as pre-moistenedwipes to be dispensed from a bathroom dispenser. The properties of eachthese wipes appear in Table 29 listed as Code L and Code R respectively.

[0306] Both codes L and R have in use CDWT strength greater than 100g/1″ combined with a wet thickness greater than 0.3 mm, a wetopacity >35%, a wet cup crush lest than 40 g and soaked CDWTs less than30 g/1″ after soaking in solutions of either 10 ppm or 200 ppm of 2:1Ca++/Mg++ for 1 hour.

EXAMPLE 44

[0307] A 55 gsm, airlaid substrate was created using the methods ofExample 42 except that 15 weight % of the fiber furnish consisted of 6mm, crimped PET fibers (KOSA). The binder level, binders, binder blend,and dry sheet thickness were the same as those in Example 42. Some ofthe dried web was slit to 4.25-inch width and treated with the wettingsolution of Example 18 at 225% add-on. The moistened web was convertedinto a coreless, perforated roll form for use as pre-moistened wipes tobe dispensed from a bathroom dispenser. The properties of these wipesappear in Table 29 listed as Code J.

[0308] Code J has an in use CD wet tensile >100 g/1″, a wet sheetthickness >0.3 mm, an wet opacity greater than 35%, a wet cup crush lessthan 40 g and excellent hard water dispersibility (6% of original CDWT).It has CDWTs of less than 30 g/1″ after soaking in waters containingeither 10 ppm or 200 ppm of a 2:1 Ca++/Mg++.

EXAMPLE 45

[0309] A 65 gsm substrate containing 22% binder was prepared on acommercial airlaid machine having a DanWeb airlaid former using twoforming heads. Weyerhaeuser CF405 bleached softwood kraft fiber in rollpulp form was used and fiberized with hammermills, then formed into a50.7 gsm airlaid web on the moving wire. The newly formed web wasdensified by heated compaction rolls and transferred to a second wire,where the web was further densified by a second heated compaction roll.The web was then transferred and uniformly sprayed on the top side withion-sensitive polymer formulation mixture on the exposed surface of theweb, applying half of the ion-sensitive polymer formulation solids (7.2gsm) relative to the dry fiber mass of the finished substrate weight.

[0310] The ion-sensitive polymer formulation mixture comprised water asthe carrier with 15% binder solids, wherein the binder comprised 75%SSB-6 as the ion-sensitive polymer formulation and 25% Dur-O-SET® RB(National Starch) as the co-binder polymer.

[0311] After the web was sprayed, it was carried into an oven to dry thebinder solution. The web then was transferred onto another wire and theunderside of the sheet uniformly sprayed with the ion sensitive polymerformulation. The remaining half of the ion sensitive polymer formulationsolids (7.2 gsm) relative to dry fiber mass of the finished substrateweight was applied.

[0312] After the second binder application, the web was again carriedinto an oven to dry the newly applied binder solution. The airtemperature in the ovens was approximately 190° C. to 205° C.

[0313] The average basis weight of the web after drying was 65.1 gsm.The average thickness of the dry web was 0.86 mm. The machine directiondry tensile (MDDT) strength of the web was measured at 2468 g/1″ with aMD dry stretch of 9.7%.

[0314] The dried web was converted into a coreless, perforated roll formfor use as a pre-moistened wipe using the wetting solution of Example 39at an add-on of 250%. The properties of these wipes appear in Table 29listed as CFR.

[0315] As shown in Table 29 these wipes have excellent dispersibility ineither 10 ppm or 200 ppm 2:1 Ca++/Mg++ solutions. The wet wipes alsohave very good in use, wet sheet thickness, wet opacity, and wet cupcrush properties.

COMPARATIVE EXAMPLE 46

[0316] A 68 gsm airlaid web was prepared according to the methodsExample 10. The web was not humidified between heated compaction rolls.The pulp web was sprayed with a 100% Lion SSB-3b acrylic-acid basedbinder (LION Corporation, Tokyo, Japan) at 15% spray solids. Thethickness of the web after drying was 1.6 mm. The web had a machinedirection dry tensile of 3.48 kg/3″.

[0317] Sheets of the dry web were cut and subsequently wetted by thehand rolling method to a wetting solution add-on of 200% using asolution containing 0.9% NaCl, 0.5% phospholipid CDM (Mona), and 0.5%Mackstat H-66. The properties of this pre-moistened wipe were measuredand appear in Table 29 coded as 1312.

[0318] Although this prototype has very good in use strength (CDWT),thickness, opacity and cup crush properties, its soaked tensile strengthis very sensitive to the water in which it is soaked. This prototype hasa S-CDWT after one hour in hard water dipsersibility of 80% of theoriginal in-use wet strength and is therefore not dispersible in hardwater. In the 10 ppm soaking solution it has a CDWT >30 g/1″. In the 200ppm soaking solution it has a CDWT of 355 g/1″ after 1 hour.

COMPARATIVE EXAMPLE 47

[0319] A 68 gsm airlaid web was prepared according to the methodsExample 10. The web was not humidified between heated compaction rolls.The pulp web was sprayed with binder blend comprising 85% Lion SSB-3bacrylic-acid based binder (LION Corporation, Tokyo, Japan) and 15%Dur-O-Set® RB adjusted to a final spray solids of 15%. The thickness ofthe web after drying was 1.5 mm. The web had a machine direction drytensile of 1.8 kg/3″.

[0320] Sheets of the dry web were cut and subsequently wetted using ahand spray application of a wetting solution containing 0.9% NaCl, 0.5%phospholipid CDM (Mona), and 0.5% Mackstat H-66. The wetting solutionadd-on was 200%. The properties of this pre-moistened wipe were measuredand appear in Table 29 coded as 1308.

[0321] Although this prototype also has very good in use strength(CDWT), thickness, opacity and cup crush properties, its soaked tensilestrength is very sensitive to the water in which it is soaked. In the 10ppm soaking solution it had a CDWT of 78 g/1″. In the 200 ppm soakingsolution it had a CDWT of 322 g/1″ after 1 hour. TABLE 29 ComparativeTesting Results S-CDWT S-CDWT Percent Sheet Cup Cup Crush Example,Description and CDWT 1 hr in 10 1 hr in 200 CDWT after 1 ThicknessOpacity Crush Peak Designation (g/in²) ppm (g/in) ppm (g/in) hr in 200ppm (%) (mm) (%) (g-mm) Load (gm) Format Example 40 159 8 16 10 0.7545.6 104 15.1 60 gsm, 100% pulp, 75/25, 20% binder, 1.2 mm; Code 3007Example 40 427 26 30 7 0.55 42.6 170 24.1 60 gsm, 100% pulp, 75/25, 20%binder, 0.8 mm; Code 3010 Example 41 308 x 1 0.3 0.46 44.5 174 25.7 63gsm, 100% pulp, 75/25, 20% binder, 1.3 mm; Code E Example 42 541 19.624.9 5 0.46 44.5 207 29.6 65 gsm, 100% pulp, 75/25, 22% binder (2905);Code G Example 44 276 8.1 16.3 6 0.39 38.1 192 27 55 gsm, 90/10 PET,75/25, 20% binder (2910); Code J Example 43 253 26.4 19.4 8 0.40 41.6194 28.8 60 gsm, 100% pulp, 75/25, 20% binder (2908); Code L Example 43292 16.5 25.4 9 0.40 40.5 172 26.1 55 gsm, 100% pulp, 75/25, 20% binder(2909); Code R Example 45 291 0 0 0 0.44 41.9 316 26.4 Roll 65 gsm, 100%pulp, 75/25, 22% binder, 0.9 m; Code CFR Comparative Example 46 411 57280 80 0.46 46.8 195 30 68 gsm, 100% pulp, 100% Lion SSB, 20% binder(1312); Code 1312 Comparative Example 47 345 78 322 93 0.81 52.8 62/46114/29.2 68 gsm, 100% pulp, 75/25 Lion SSB, 20% binder (1308); Code 1308Comparative Example 35 336 339 320 95 0.62 47.9 499 27.9 FoldedCottonelle Fresh Folded, Code KCF Comparative Example 35 391 392 380 970.63 45.9 613 32.2 Folded Just For Me; Code JFM Comparative Example 35241 250 240 100 0.77 46.7 304 26.2 Folded Charmin Kid Fresh; Code CHFComparative Example 36 272 118 117 43 0.61 44.7 125 15.8 Roll MoistMates 1997; Code MM-1 Comparative Example 36 234 242 234 100 0.59 40.1155 19.6 Roll Moist Mates; Code MM-2 Comparative Example 37 289 0 0 00.45 33.8 200 25.1 Folded Merries Flushable Baby Wipes; Code KaoComparative Example 38 106 70 70 66 0.52 42.7 129 10.5 Folded Pigeon;Code Pigeon

[0322] It should be understood that the foregoing relates only tocertain disclosed embodiments of the present invention and that numerousmodifications or alterations may be made therein without departing fromthe spirit and scope of the invention as set forth in the appendedclaims.

What is claimed is:
 1. A wet wipe having an in-use tensile strength of greater than about 100 g/in, wherein the wet wipe has a tensile strength of less than about 70 g/in after being soaked in water having a concentration of about 10 ppm of one or more multivalent ions for about one hour, wherein the wet wipe has a tensile strength of less than about 60% of the in-use tensile strength after being soaked in water having a concentration of about 200 ppm of one or more multivalent ions for about one hour, wherein the wet wipe has an opacity greater than about 35%
 2. The wet wipe of claim 1, wherein the wet wipe has an in-use tensile strength of greater than about 100 g/in, a tensile strength of less than about 50 g/in after being soaked in water having a concentration of about 10 ppm of one or more multivalent ions for about one hour and a tensile strength of less than about 40% of the in-use tensile strength after being soaked in water having a concentration of about 200 ppm of one or more multivalent ions for about one hour.
 3. The wet wipe of claim 1, wherein the wet wipe has an in-use tensile strength of greater than about 100 g/in, a tensile strength of less than about 30 g/in after being soaked in water having a concentration of about 10 ppm of one or more multivalent ions for about one hour and a tensile strength of less than about 20% of the in-use tensile strength after being soaked in water having a concentration of about 200 ppm of one or more multivalent ions for about one hour.
 4. The wet wipe of claim 1, wherein the wet wipe has an in-use tensile strength of greater than about 200 g/in, a tensile strength of less than about 50 g/in after being soaked in water having a concentration of about 10 ppm of one or more multivalent ions for about one hour and a tensile strength of less than about 40% of the in-use tensile strength after being soaked in water having a concentration of about 200 ppm of one or more multivalent ions for about one hour.
 5. The wet wipe of claim 1, wherein the wet wipe has an in-use tensile strength of greater than about 200 g/in, a tensile strength of less than about 30 g/in after being soaked in water having a concentration of about 10 ppm of one or more multivalent ions for about one hour and a tensile strength of less than about 20% of the in-use tensile strength after being soaked in water having a concentration of about 200 ppm of one or more multivalent ions for about one hour.
 6. The wet wipe of claim 1, wherein the wet wipe has an in-use tensile strength of greater than about 300 g/in, a tensile strength of less than about 50 g/in after being soaked in water having a concentration of about 10 ppm of one or more multivalent ions for about one hour and a tensile strength of less than about 40% of the in-use tensile strength after being soaked in water having a concentration of about 200 ppm of one or more multivalent ions for about one hour.
 7. The wet wipe of claim 1, wherein the wet wipe has an in-use tensile strength of greater than about 300 g/in, a tensile strength of less than about 30 g/in after being soaked in water having a concentration of about 10 ppm of one or more multivalent ions for about one hour and a tensile strength of less than about 20% of the in-use tensile strength after being soaked in water having a concentration of about 200 ppm of one or more multivalent ions for about one hour.
 8. The wet wipe of claim 1, wherein the wet wipe has a thickness greater than about 0.25 mm.
 9. The wet wipe of claim 1, wherein the wet wipe has a thickness greater than about 0.3 mm.
 10. The wet wipe of claim 1, wherein the wet wipe has a thickness greater than about 0.4 mm.
 11. The wet wipe of claim 1, wherein the wet wipe has a cup crush less than about 40 g.
 12. The wet wipe of claim 1, wherein the wet wipe has a cup crush less than about 25 g.
 13. The wet wipe of claim 1, wherein the wet wipe has a cup crush less than about 10 g.
 14. The wet wipe of claim 1, wherein the wet wipe comprises a fabric sheet saturated with a wetting composition, wherein the fabric sheet comprises fibrous material and an ion-sensitive binder, and wherein the wetting composition contains less than about 5 weight percent of organic solvents.
 15. The wet wipe of claim 14, wherein the wetting composition contains less than about 3 weight percent of organic solvents.
 16. The wet wipe of claim 15, wherein the wetting composition contains less than about 1 weight percent of organic solvents.
 17. The wet wipe of claim 14, wherein the wetting composition is substantially free of organic solvents.
 18. The wet wipe of claim 14, wherein the wetting composition comprises an activating compound at a concentration of at least 1 weight percent based on the weight of the wetting composition.
 19. The wet wipe of claim 18, wherein the activating compound comprises a monovalent salt and is present at a concentration of at least 1 weight percent based on the weight of the wetting composition.
 20. The wet wipe of claim 19, wherein the activating compound is present at a concentration of from about 1 weight percent to about 10 weight percent based on the weight of the wetting composition.
 21. The wet wipe of claim 20, wherein the activating compound is present at a concentration of from about 1 weight percent to about 5 weight percent based on the weight of the wetting composition.
 22. The wet wipe of claim 21, wherein the activating compound is present at a concentration of about 4 weight percent.
 23. The wet wipe of claim 18, wherein the activating compound is sodium chloride.
 24. The wet wipe of claim 14, wherein the ion-sensitive binder comprises at least one of an ion-sensitive polymer and a co-binder.
 25. The wet wipe of claim 24, wherein the ion-sensitive polymer is formed from (a) at least one of acrylic acid and methacrylic acid, and (b) one or more alkyl acrylates.
 26. The wet wipe of claim 24, wherein the ion-sensitive polymer is formed from one or more monomers selected from acrylic acid; 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS); the sodium salt of 2-acrylamido-2-methyl-1-propanesulfonic acid (NaAMPS); butyl acrylate; and 2-ethylhexyl acrylate.
 27. The wet wipe of claim 24, wherein the co-binder is selected from non-crosslinking poly(ethylene-vinyl acetate), non-crosslinking poly(styrene-butadiene), and non-crosslinking poly(styrene-acrylic).
 28. The wet wipe of claim 27, wherein the co-binder is non-crosslinking poly(ethylene-vinyl acetate).
 29. The wet wipe of claim 14, wherein the wetting composition comprises: about 86 to about 98 weight percent deionized water; about 1 to about 6 weight percent sodium chloride as the activating compound; up to about 2 weight percent of one or more preservatives; up to about 2 weight percent of one or more surfactants; up to about 1 weight percent of one or more silicone emulsions; up to about 1 weight percent of one or more emollients; up to about 0.3 weight percent of one or more fragrances; up to about 0.5 weight percent of one or more fragrance solubilizers; and up to about 0.5 weight percent of one or more pH adjusters.
 30. The wet wipe of claim 29, wherein the wetting composition comprises: about 86 to about 98 weight percent of deionized water; about 1 to about 6 weight percent of sodium chloride as the activating compound; from greater than 0 to about 2 weight percent of one or more preservatives comprising glycerin, iodopropynyl butylcarbamate (IPBC), and dimethyloldimethyl (DMDM) hydantoin; from greater than 0 to about 2 weight percent of a surfactant comprising acyl glutamate; from greater than 0 to about 1 weight percent of one or more silicone emulsions comprising dimethiconol and triethanolamine (TEA) dodecylbenezene sulfonate; from greater than 0 to about 1 weight percent of an emollient comprising PEG-75 Lanolin; from greater than 0 to about 0.3 weight percent of one or more fragrances; from greater than 0 to about 0.5 weight percent of a fragrance solubilizer comprising polysorbate 20; and from greater than 0 to about 0.2 weight percent of a pH adjuster comprising malic acid.
 31. The wet wipe of claim 30, wherein the wetting composition comprises: about 92.88 weight percent of deionized water; about 4.00 weight percent of sodium chloride as the activating compound; about 1.00 weight percent of one or more preservatives comprising glycerin, IPBC, and DMDM hydantoin; about 1.00 weight percent of a surfactant comprising acyl glutamate; about 0.50 weight percent of one or more silicone emulsions comprising dimethiconol and TEA dodecylbenezene sulfonate; about 0.25 weight percent of an emollient comprising PEG-75 Lanolin; about 0.05 weight percent of one or more fragrances; about 0.25 weight percent of a fragrance solubilizer comprising polysorbate 20; and about 0.07 weight percent of a pH adjuster comprising malic acid.
 32. A wet wipe comprising a fabric sheet saturated with a wetting composition, wherein the fabric sheet comprises fibrous material and an ion-sensitive binder, and wherein the wetting composition contains less than about 5 weight percent of organic solvents; wherein the wet wipe has an in-use tensile strength of greater than about 100 g/in, wherein the wet wipe has a tensile strength of less than about 70 g/in after being soaked in water having a concentration of about 10 ppm of one or more multivalent ions for about one hour, wherein the wet wipe has a tensile strength of less than about 60% of the in-use tensile strength after being soaked in water having a concentration of about 200 ppm of one or more multivalent ions for about one hour.
 33. The wet wipe of claim 32, wherein the fibrous material comprises one or more layers of a woven fabric, a nonwoven fabric, a knitted fabric, or a combination thereof.
 34. The wet wipe of claim 32, wherein the fibrous material comprises one or more layers of a nonwoven fabric.
 35. The wet wipe of claim 32, wherein the fibrous material comprises fibers having a length of about 15 mm or less.
 36. The wet wipe of claim 32, wherein the fibrous material comprises natural fibers, synthetic fibers, or a combination thereof.
 37. The wet wipe of claim 32, wherein the fibrous material comprises one or more fibers containing cotton, linen, jute, hemp, wool, wood pulp, viscose rayon, cuprammonium rayon, cellulose acetate, polyester, polyamide, and polyacrylic.
 38. The wet wipe of claim 32, wherein the fibrous material comprises wood pulp.
 39. The wet wipe of claim 32, wherein the wet wipe has an in-use tensile strength of greater than about 100 g/in, a tensile strength of less than about 50 g/in after being soaked in water having a concentration of about 10 ppm of one or more multivalent ions for about one hour and a tensile strength of less than about 40% of the in-use tensile strength after being soaked in water having a concentration of about 200 ppm of one or more multivalent ions for about one hour.
 40. The wet wipe of claim 32, wherein the wet wipe has an in-use tensile strength of greater than about 100 g/in, a tensile strength of less than about 30 g/in after being soaked in water having a concentration of about 10 ppm of one or more multivalent ions for about one hour and a tensile strength of less than about 20% of the in-use tensile strength after being soaked in water having a concentration of about 200 ppm of one or more multivalent ions for about one hour.
 41. The wet wipe of claim 32, wherein the wet wipe has an in-use tensile strength of greater than about 200 g/in, a tensile strength of less than about 50 g/in after being soaked in water having a concentration of about 10 ppm of one or more multivalent ions for about one hour and a tensile strength of less than about 40% of the in-use tensile strength after being soaked in water having a concentration of about 200 ppm of one or more multivalent ions for about one hour.
 42. The wet wipe of claim 32, wherein the wet wipe has an in-use tensile strength of greater than about 200 g/in, a tensile strength of less than about 30 g/in after being soaked in water having a concentration of about 10 ppm of one or more multivalent ions for about one hour and a tensile strength of less than about 20% of the in-use tensile strength after being soaked in water having a concentration of about 200 ppm of one or more multivalent ions for about one hour.
 43. The wet wipe of claim 32, wherein the wet wipe has an in-use tensile strength of greater than about 300 g/in, a tensile strength of less than about 50 g/in after being soaked in water having a concentration of about 10 ppm of one or more multivalent ions for about one hour and a tensile strength of less than about 40% of the in-use tensile strength after being soaked in water having a concentration of about 200 ppm of one or more multivalent ions for about one hour.
 44. The wet wipe of claim 32, wherein the wet wipe has an in-use tensile strength of greater than about 300 g/in, a tensile strength of less than about 30 g/in after being soaked in water having a concentration of about 10 ppm of one or more multivalent ions for about one hour and a tensile strength of less than about 20% of the in-use tensile strength after being soaked in water having a concentration of about 200 ppm of one or more multivalent ions for about one hour.
 45. The wet wipe of claim 32, wherein the wet wipe has a thickness greater than about 0.25 mm.
 46. The wet wipe of claim 32, wherein the wet wipe has a thickness greater than about 0.3 mm.
 47. The wet wipe of claim 32, wherein the wet wipe has a thickness greater than about 0.4 mm.
 48. The wet wipe of claim 32, wherein the wet wipe has a cup crush less than about 40 g.
 49. The wet wipe of claim 32, wherein the wet wipe has a cup crush less than about 25 g.
 50. The wet wipe of claim 32, wherein the wet wipe has a cup crush less than about 10 g.
 51. The wet wipe of claim 32, wherein the wetting composition contains less than about 3 weight percent of organic solvents.
 52. The wet wipe of claim 51, wherein the wetting composition contains less than about 1 weight percent of organic solvents.
 53. The wet wipe of claim 52, wherein the wetting composition is substantially free of organic solvents.
 54. The wet wipe of claim 32, wherein the wet wipe has an opacity greater than about 20%.
 55. The wet wipe of claim 32, wherein the wet wipe has an opacity greater than about 35%. 